Merge pull request #2679 from Hixie/overrides

Add @override annotations to flutter framework

dev/manual_tests/card_collection.dart

@@ -17,6 +17,7 @@ class CardModel {
 }
 
 class CardCollection extends StatefulWidget {
+  @override
   CardCollectionState createState() => new CardCollectionState();
 }
 
@@ -72,6 +73,7 @@ class CardCollectionState extends State<CardCollection> {
       _initVariableSizedCardModels();
   }
 
+  @override
   void initState() {
     super.initState();
     _initCardModels();
@@ -403,6 +405,7 @@ class CardCollectionState extends State<CardCollection> {
     .createShader(bounds);
   }
 
+  @override
   Widget build(BuildContext context) {
     Widget cardCollection;
     if (_fixedSizeCards) {

dev/manual_tests/drag_and_drop.dart

@@ -7,6 +7,7 @@ import 'dart:math' as math;
 import 'package:flutter/material.dart';
 
 class ExampleDragTarget extends StatefulWidget {
+  @override
   ExampleDragTargetState createState() => new ExampleDragTargetState();
 }
 
@@ -19,6 +20,7 @@ class ExampleDragTargetState extends State<ExampleDragTarget> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new DragTarget<Color>(
       onAccept: _handleAccept,
@@ -41,14 +43,19 @@ class ExampleDragTargetState extends State<ExampleDragTarget> {
 
 class Dot extends StatefulWidget {
   Dot({ Key key, this.color, this.size, this.child, this.tappable: false }) : super(key: key);
+
   final Color color;
   final double size;
   final Widget child;
   final bool tappable;
+
+  @override
   DotState createState() => new DotState();
 }
 class DotState extends State<Dot> {
   int taps = 0;
+
+  @override
   Widget build(BuildContext context) {
     return new GestureDetector(
       onTap: config.tappable ? () { setState(() { taps += 1; }); } : null,
@@ -84,6 +91,7 @@ class ExampleDragSource extends StatelessWidget {
   static const double kHeavyMultiplier = 1.5;
   static const double kFingerSize = 50.0;
 
+  @override
   Widget build(BuildContext context) {
     double size = kDotSize;
     if (heavy)
@@ -146,6 +154,7 @@ class DashOutlineCirclePainter extends CustomPainter {
   static const double segmentArc = deltaTheta / 2.0; // radians
   static const double startOffset = 1.0; // radians
 
+  @override
   void paint(Canvas canvas, Size size) {
     final double radius = size.shortestSide / 2.0;
     final Paint paint = new Paint()
@@ -159,6 +168,7 @@ class DashOutlineCirclePainter extends CustomPainter {
     canvas.drawPath(path, paint);
   }
 
+  @override
   bool shouldRepaint(DashOutlineCirclePainter oldPainter) => false;
 }
 
@@ -172,6 +182,7 @@ class MovableBall extends StatelessWidget {
   static final GlobalKey kBallKey = new GlobalKey();
   static const double kBallSize = 50.0;
 
+  @override
   Widget build(BuildContext context) {
     Widget ball = new DefaultTextStyle(
       style: Theme.of(context).textTheme.body1.copyWith(
@@ -213,14 +224,18 @@ class MovableBall extends StatelessWidget {
 }
 
 class DragAndDropApp extends StatefulWidget {
+  @override
   DragAndDropAppState createState() => new DragAndDropAppState();
 }
 
 class DragAndDropAppState extends State<DragAndDropApp> {
   int position = 1;
+
   void moveBall(int newPosition) {
     setState(() { position = newPosition; });
   }
+
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(

dev/manual_tests/mozart.dart

@@ -46,6 +46,7 @@ class WindowDecoration extends StatelessWidget {
   final GestureTapCallback onTap;
   final GesturePanUpdateCallback onPanUpdate;
 
+  @override
   Widget build(BuildContext context) {
     double top, right, bottom, left, width, height;
 
@@ -93,6 +94,7 @@ class Window extends StatefulWidget {
   final ChildViewConnection child;
   final ValueChanged<ChildViewConnection> onClose;
 
+  @override
   _WindowState createState() => new _WindowState();
 }
 
@@ -119,6 +121,7 @@ class _WindowState extends State<Window> {
     config.onClose(config.child);
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Positioned(
       left: _offset.dx,
@@ -167,6 +170,7 @@ class LauncherItem extends StatelessWidget {
   final Widget child;
   final ValueChanged<ChildViewConnection> onLaunch;
 
+  @override
   Widget build(BuildContext context) {
     return new RaisedButton(
       onPressed: () { onLaunch(new ChildViewConnection(url: url)); },
@@ -180,6 +184,7 @@ class Launcher extends StatelessWidget {
 
   final List<Widget> items;
 
+  @override
   Widget build(BuildContext context) {
     return new Row(
       mainAxisAlignment: MainAxisAlignment.center,
@@ -189,6 +194,7 @@ class Launcher extends StatelessWidget {
 }
 
 class WindowManager extends StatefulWidget {
+  @override
   _WindowManagerState createState() => new _WindowManagerState();
 }
 
@@ -207,6 +213,7 @@ class _WindowManagerState extends State<WindowManager> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Material(
       child: new Stack(

dev/manual_tests/overlay_geometry.dart

@@ -27,6 +27,7 @@ class _MarkerPainter extends CustomPainter {
   final double size;
   final MarkerType type;
 
+  @override
   void paint(Canvas canvas, _) {
     Paint paint = new Paint()..color = const Color(0x8000FF00);
     double r = size / 2.0;
@@ -46,6 +47,7 @@ class _MarkerPainter extends CustomPainter {
     }
   }
 
+  @override
   bool shouldRepaint(_MarkerPainter oldPainter) {
     return oldPainter.size != size
         || oldPainter.type != type;
@@ -64,6 +66,7 @@ class Marker extends StatelessWidget {
   final double size;
   final MarkerType type;
 
+  @override
   Widget build(BuildContext context) {
     return new Positioned(
       left: position.x - size / 2.0,
@@ -83,6 +86,7 @@ class Marker extends StatelessWidget {
 }
 
 class OverlayGeometryApp extends StatefulWidget {
+  @override
   OverlayGeometryAppState createState() => new OverlayGeometryAppState();
 }
 
@@ -96,6 +100,7 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
   double markersScrollOffset;
   ScrollListener scrollListener;
 
+  @override
   void initState() {
     super.initState();
     List<double> cardHeights = <double>[
@@ -151,6 +156,7 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> layers = <Widget>[
       new Scaffold(

dev/manual_tests/pageable_list.dart

@@ -14,10 +14,12 @@ class CardModel {
 }
 
 class PageableListApp extends StatefulWidget {
+  @override
   PageableListAppState createState() => new PageableListAppState();
 }
 
 class PageableListAppState extends State<PageableListApp> {
+  @override
   void initState() {
     super.initState();
     List<Size> cardSizes = [
@@ -122,6 +124,7 @@ class PageableListAppState extends State<PageableListApp> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new IconTheme(
       data: const IconThemeData(color: Colors.white),

dev/manual_tests/raw_keyboard.dart

@@ -33,6 +33,7 @@ void main() {
 class RawKeyboardDemo extends StatefulWidget {
   RawKeyboardDemo({ GlobalKey key }) : super(key: key);
 
+  @override
   _HardwareKeyDemoState createState() => new _HardwareKeyDemoState();
 }
 
@@ -45,6 +46,7 @@ class _HardwareKeyDemoState extends State<RawKeyboardDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context)  {
     bool focused = Focus.at(context);
     Widget child;

examples/layers/rendering/autolayout.dart

@@ -14,6 +14,7 @@ class _MyAutoLayoutDelegate extends AutoLayoutDelegate {
   AutoLayoutRect p3 = new AutoLayoutRect();
   AutoLayoutRect p4 = new AutoLayoutRect();
 
+  @override
   List<al.Constraint> getConstraints(AutoLayoutRect parent) {
     return <al.Constraint>[
       // Sum of widths of each box must be equal to that of the container
@@ -44,6 +45,7 @@ class _MyAutoLayoutDelegate extends AutoLayoutDelegate {
     ];
   }
 
+  @override
   bool shouldUpdateConstraints(AutoLayoutDelegate oldDelegate) => true;
 }
 

examples/layers/rendering/src/sector_layout.dart

@@ -36,9 +36,13 @@ class SectorConstraints extends Constraints {
     return deltaTheta.clamp(minDeltaTheta, maxDeltaTheta);
   }
 
+  @override
   bool get isTight => minDeltaTheta >= maxDeltaTheta && minDeltaTheta >= maxDeltaTheta;
 
+  @override
   bool get isNormalized => minDeltaRadius <= maxDeltaRadius && minDeltaTheta <= maxDeltaTheta;
+
+  @override
   bool get debugAssertIsNormalized {
     assert(isNormalized);
     return isNormalized;
@@ -69,6 +73,7 @@ class SectorParentData extends ParentData {
 
 abstract class RenderSector extends RenderObject {
 
+  @override
   void setupParentData(RenderObject child) {
     if (child.parentData is! SectorParentData)
       child.parentData = new SectorParentData();
@@ -76,13 +81,17 @@ abstract class RenderSector extends RenderObject {
 
   // RenderSectors always use SectorParentData subclasses, as they need to be
   // able to read their position information for painting and hit testing.
+  @override
   SectorParentData get parentData => super.parentData;
 
   SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
     return new SectorDimensions.withConstraints(constraints);
   }
 
+  @override
   SectorConstraints get constraints => super.constraints;
+
+  @override
   void debugAssertDoesMeetConstraints() {
     assert(constraints != null);
     assert(deltaRadius != null);
@@ -94,11 +103,15 @@ abstract class RenderSector extends RenderObject {
     assert(constraints.minDeltaTheta <= deltaTheta);
     assert(deltaTheta <= math.max(constraints.minDeltaTheta, constraints.maxDeltaTheta));
   }
+
+  @override
   void performResize() {
     // default behavior for subclasses that have sizedByParent = true
     deltaRadius = constraints.constrainDeltaRadius(0.0);
     deltaTheta = constraints.constrainDeltaTheta(0.0);
   }
+
+  @override
   void performLayout() {
     // descendants have to either override performLayout() to set both
     // the dimensions and lay out children, or, set sizedByParent to
@@ -106,7 +119,10 @@ abstract class RenderSector extends RenderObject {
     assert(sizedByParent);
   }
 
+  @override
   Rect get paintBounds => new Rect.fromLTWH(0.0, 0.0, 2.0 * deltaRadius, 2.0 * deltaRadius);
+
+  @override
   Rect get semanticBounds => new Rect.fromLTWH(-deltaRadius, -deltaRadius, 2.0 * deltaRadius, 2.0 * deltaRadius);
 
   bool hitTest(HitTestResult result, { double radius, double theta }) {
@@ -137,6 +153,7 @@ abstract class RenderDecoratedSector extends RenderSector {
   }
 
   // offset must point to the center of the circle
+  @override
   void paint(PaintingContext context, Offset offset) {
     assert(deltaRadius != null);
     assert(deltaTheta != null);
@@ -167,6 +184,7 @@ class SectorChildListParentData extends SectorParentData with ContainerParentDat
 class RenderSectorWithChildren extends RenderDecoratedSector with ContainerRenderObjectMixin<RenderSector, SectorChildListParentData> {
   RenderSectorWithChildren(BoxDecoration decoration) : super(decoration);
 
+  @override
   void hitTestChildren(HitTestResult result, { double radius, double theta }) {
     RenderSector child = lastChild;
     while (child != null) {
@@ -177,6 +195,7 @@ class RenderSectorWithChildren extends RenderDecoratedSector with ContainerRende
     }
   }
 
+  @override
   void visitChildren(RenderObjectVisitor visitor) {
     RenderSector child = lastChild;
     while (child != null) {
@@ -217,12 +236,14 @@ class RenderSectorRing extends RenderSectorWithChildren {
     }
   }
 
+  @override
   void setupParentData(RenderObject child) {
     // TODO(ianh): avoid code duplication
     if (child.parentData is! SectorChildListParentData)
       child.parentData = new SectorChildListParentData();
   }
 
+  @override
   SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
     double outerDeltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
     double innerDeltaRadius = outerDeltaRadius - padding * 2.0;
@@ -251,6 +272,7 @@ class RenderSectorRing extends RenderSectorWithChildren {
                                                 deltaTheta: innerTheta);
   }
 
+  @override
   void performLayout() {
     assert(this.parentData is SectorParentData);
     deltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
@@ -284,6 +306,7 @@ class RenderSectorRing extends RenderSectorWithChildren {
 
   // offset must point to the center of our circle
   // each sector then knows how to paint itself at its location
+  @override
   void paint(PaintingContext context, Offset offset) {
     // TODO(ianh): avoid code duplication
     super.paint(context, offset);
@@ -327,12 +350,14 @@ class RenderSectorSlice extends RenderSectorWithChildren {
     }
   }
 
+  @override
   void setupParentData(RenderObject child) {
     // TODO(ianh): avoid code duplication
     if (child.parentData is! SectorChildListParentData)
       child.parentData = new SectorChildListParentData();
   }
 
+  @override
   SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
     assert(this.parentData is SectorParentData);
     double paddingTheta = math.atan(padding / this.parentData.radius);
@@ -359,6 +384,7 @@ class RenderSectorSlice extends RenderSectorWithChildren {
                                                 deltaTheta: outerDeltaTheta);
   }
 
+  @override
   void performLayout() {
     assert(this.parentData is SectorParentData);
     deltaTheta = constraints.constrainDeltaTheta(desiredDeltaTheta);
@@ -389,6 +415,7 @@ class RenderSectorSlice extends RenderSectorWithChildren {
 
   // offset must point to the center of our circle
   // each sector then knows how to paint itself at its location
+  @override
   void paint(PaintingContext context, Offset offset) {
     // TODO(ianh): avoid code duplication
     super.paint(context, offset);
@@ -417,29 +444,34 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
     markNeedsLayout();
   }
 
+  @override
   void setupParentData(RenderObject child) {
     if (child.parentData is! SectorParentData)
       child.parentData = new SectorParentData();
   }
 
+  @override
   double getMinIntrinsicWidth(BoxConstraints constraints) {
     if (child == null)
       return super.getMinIntrinsicWidth(constraints);
     return getIntrinsicDimensions(constraints).width;
   }
 
+  @override
   double getMaxIntrinsicWidth(BoxConstraints constraints) {
     if (child == null)
       return super.getMaxIntrinsicWidth(constraints);
     return getIntrinsicDimensions(constraints).width;
   }
 
+  @override
   double getMinIntrinsicHeight(BoxConstraints constraints) {
     if (child == null)
       return super.getMinIntrinsicHeight(constraints);
     return getIntrinsicDimensions(constraints).height;
   }
 
+  @override
   double getMaxIntrinsicHeight(BoxConstraints constraints) {
     if (child == null)
       return super.getMaxIntrinsicHeight(constraints);
@@ -456,6 +488,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
     return constraints.constrain(new Size(dimension, dimension));
   }
 
+  @override
   void performLayout() {
     if (child == null) {
       size = constraints.constrain(Size.zero);
@@ -472,6 +505,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
     }
   }
 
+  @override
   void paint(PaintingContext context, Offset offset) {
     super.paint(context, offset);
     if (child != null) {
@@ -481,6 +515,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
     }
   }
 
+  @override
   bool hitTest(HitTestResult result, { Point position }) {
     if (child == null)
       return false;
@@ -516,15 +551,18 @@ class RenderSolidColor extends RenderDecoratedSector {
   double desiredDeltaTheta;
   final Color backgroundColor;
 
+  @override
   SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
     return new SectorDimensions.withConstraints(constraints, deltaTheta: desiredDeltaTheta);
   }
 
+  @override
   void performLayout() {
     deltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
     deltaTheta = constraints.constrainDeltaTheta(desiredDeltaTheta);
   }
 
+  @override
   void handleEvent(PointerEvent event, HitTestEntry entry) {
     if (event is PointerDownEvent) {
       decoration = new BoxDecoration(backgroundColor: const Color(0xFFFF0000));

examples/layers/rendering/src/solid_color_box.dart

@@ -13,34 +13,40 @@ class RenderSolidColorBox extends RenderDecoratedBox {
       : backgroundColor = backgroundColor,
         super(decoration: new BoxDecoration(backgroundColor: backgroundColor));
 
+  @override
   double getMinIntrinsicWidth(BoxConstraints constraints) {
     return constraints.constrainHeight(
       this.desiredSize == Size.infinite ? 0.0 : desiredSize.width
     );
   }
 
+  @override
   double getMaxIntrinsicWidth(BoxConstraints constraints) {
     return constraints.constrainWidth(
       this.desiredSize == Size.infinite ? 0.0 : desiredSize.width
     );
   }
 
+  @override
   double getMinIntrinsicHeight(BoxConstraints constraints) {
     return constraints.constrainHeight(
       this.desiredSize == Size.infinite ? 0.0 : desiredSize.height
     );
   }
 
+  @override
   double getMaxIntrinsicHeight(BoxConstraints constraints) {
     return constraints.constrainHeight(
       this.desiredSize == Size.infinite ? 0.0 : desiredSize.height
     );
   }
 
+  @override
   void performLayout() {
     size = constraints.constrain(desiredSize);
   }
 
+  @override
   void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
     if (event is PointerDownEvent) {
       decoration = new BoxDecoration(backgroundColor: const Color(0xFFFF0000));

examples/layers/rendering/touch_input.dart

@@ -45,20 +45,24 @@ class RenderDots extends RenderBox {
 
   /// Indicates that the size of this render object depends only on the
   /// layout constraints provided by the parent.
+  @override
   bool get sizedByParent => true;
 
   /// By selecting the biggest value permitted by the incomming constraints
   /// during layout, this function makes this render object as large as
   /// possible (i.e., fills the entire screen).
+  @override
   void performResize() {
     size = constraints.biggest;
   }
 
   /// Makes this render object hittable so that it receives pointer events.
+  @override
   bool hitTestSelf(Point position) => true;
 
   /// Processes pointer events by mutating state and invalidating its previous
   /// painting commands.
+  @override
   void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
     if (event is PointerDownEvent) {
       Color color = _kColors[event.pointer.remainder(_kColors.length)];
@@ -78,6 +82,7 @@ class RenderDots extends RenderBox {
   }
 
   /// Issues new painting commands.
+  @override
   void paint(PaintingContext context, Offset offset) {
     final Canvas canvas = context.canvas;
     // The "size" property indicates the size of that this render box was

examples/layers/services/media_service.dart

@@ -74,6 +74,7 @@ class PianoApp extends StatelessWidget {
     }
   }
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> children = <Widget>[];
     for (PianoKey key in keys) {

examples/layers/widgets/autolayout.dart

@@ -13,6 +13,7 @@ class _MyAutoLayoutDelegate extends AutoLayoutDelegate {
   AutoLayoutRect p3 = new AutoLayoutRect();
   AutoLayoutRect p4 = new AutoLayoutRect();
 
+  @override
   List<al.Constraint> getConstraints(AutoLayoutRect parent) {
     return <al.Constraint>[
       // Sum of widths of each box must be equal to that of the container
@@ -43,16 +44,19 @@ class _MyAutoLayoutDelegate extends AutoLayoutDelegate {
     ];
   }
 
+  @override
   bool shouldUpdateConstraints(_MyAutoLayoutDelegate oldDelegate) => true;
 }
 
 class ColoredBoxes extends StatefulWidget {
+  @override
   _ColoredBoxesState createState() => new _ColoredBoxesState();
 }
 
 class _ColoredBoxesState extends State<ColoredBoxes> {
   final _MyAutoLayoutDelegate delegate = new _MyAutoLayoutDelegate();
 
+  @override
   Widget build(BuildContext context) {
     return new AutoLayout(
       delegate: delegate,

examples/layers/widgets/custom_render_box.dart

@@ -9,10 +9,12 @@ class RenderDots extends RenderConstrainedBox {
   RenderDots() : super(additionalConstraints: const BoxConstraints.expand());
 
   // Makes this render box hittable so that we'll get pointer events.
+  @override
   bool hitTestSelf(Point position) => true;
 
   final Map<int, Point> _dots = <int, Point>{};
 
+  @override
   void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
     if (event is PointerDownEvent || event is PointerMoveEvent) {
       _dots[event.pointer] = event.position;
@@ -23,6 +25,7 @@ class RenderDots extends RenderConstrainedBox {
     }
   }
 
+  @override
   void paint(PaintingContext context, Offset offset) {
     final Canvas canvas = context.canvas;
     canvas.drawRect(offset & size, new Paint()..color = new Color(0xFF0000FF));
@@ -37,6 +40,8 @@ class RenderDots extends RenderConstrainedBox {
 
 class Dots extends SingleChildRenderObjectWidget {
   Dots({ Key key, Widget child }) : super(key: key, child: child);
+
+  @override
   RenderDots createRenderObject(BuildContext context) => new RenderDots();
 }
 

examples/layers/widgets/gestures.dart

@@ -25,6 +25,7 @@ class _GesturePainter extends CustomPainter {
   final bool doubleTapEnabled;
   final bool longPressEnabled;
 
+  @override
   void paint(Canvas canvas, Size size) {
     Point center = (size.center(Point.origin).toOffset() * zoom + offset).toPoint();
     double radius = size.width / 2.0 * zoom;
@@ -42,6 +43,7 @@ class _GesturePainter extends CustomPainter {
     canvas.drawCircle(center, radius, paint);
   }
 
+  @override
   bool shouldRepaint(_GesturePainter oldPainter) {
     return oldPainter.zoom != zoom
         || oldPainter.offset != offset
@@ -55,6 +57,7 @@ class _GesturePainter extends CustomPainter {
 }
 
 class GestureDemo extends StatefulWidget {
+  @override
   _GestureDemoState createState() => new _GestureDemoState();
 }
 
@@ -134,6 +137,7 @@ class _GestureDemoState extends State<GestureDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Stack(
       children: <Widget>[

examples/layers/widgets/media_query.dart

@@ -9,6 +9,7 @@ class AdaptedListItem extends StatelessWidget {
 
   final String name;
 
+  @override
   Widget build(BuildContext context) {
     return new Row(
       children: <Widget>[
@@ -31,6 +32,7 @@ class AdaptedGridItem extends StatelessWidget {
 
   final String name;
 
+  @override
   Widget build(BuildContext context) {
     return new Card(
       child: new Column(
@@ -70,6 +72,7 @@ class AdaptiveContainer extends StatelessWidget {
 
   final List<String> names;
 
+  @override
   Widget build(BuildContext context) {
     if (MediaQuery.of(context).size.width < _kGridViewBreakpoint) {
       return new ScrollableList(

examples/layers/widgets/sectors.dart

@@ -17,6 +17,7 @@ RenderBox initCircle() {
 }
 
 class SectorApp extends StatefulWidget {
+  @override
   SectorAppState createState() => new SectorAppState();
 }
 
@@ -147,6 +148,7 @@ class SectorAppState extends State<SectorApp> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new MaterialApp(
       theme: new ThemeData.light(),

examples/layers/widgets/spinning_mixed.dart

@@ -18,7 +18,10 @@ void addFlexChildSolidColor(RenderFlex parent, Color backgroundColor, { int flex
 // Solid colour, Widget version
 class Rectangle extends StatelessWidget {
   Rectangle(this.color, { Key key }) : super(key: key);
+
   final Color color;
+
+  @override
   Widget build(BuildContext context) {
     return new Flexible(
       child: new Container(

examples/layers/widgets/spinning_square.dart

@@ -5,12 +5,14 @@
 import 'package:flutter/widgets.dart';
 
 class SpinningSquare extends StatefulWidget {
+  @override
   _SpinningSquareState createState() => new _SpinningSquareState();
 }
 
 class _SpinningSquareState extends State<SpinningSquare> {
   AnimationController _animation;
 
+  @override
   void initState() {
     super.initState();
     // We use 3600 milliseconds instead of 1800 milliseconds because 0.0 -> 1.0
@@ -21,6 +23,7 @@ class _SpinningSquareState extends State<SpinningSquare> {
     )..repeat();
   }
 
+  @override
   Widget build(BuildContext context) {
     return new RotationTransition(
       turns: _animation,

examples/layers/widgets/styled_text.dart

@@ -58,6 +58,7 @@ Widget toStyledText(String name, String text) {
 Widget toPlainText(String name, String text) => new Text(name + ":" + text);
 
 class SpeakerSeparator extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new Container(
       constraints: const BoxConstraints.expand(height: 0.0),
@@ -72,10 +73,12 @@ class SpeakerSeparator extends StatelessWidget {
 }
 
 class StyledTextDemo extends StatefulWidget {
+  @override
   _StyledTextDemoState createState() => new _StyledTextDemoState();
 }
 
 class _StyledTextDemoState extends State<StyledTextDemo> {
+  @override
   void initState() {
     super.initState();
     _toText = toStyledText;
@@ -89,6 +92,7 @@ class _StyledTextDemoState extends State<StyledTextDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> lines = _kNameLines
       .map((List<String> nameAndText) => Function.apply(_toText, nameAndText))

examples/material_gallery/lib/demo/buttons_demo.dart

@@ -45,6 +45,7 @@ class _ButtonDemo {
   // to recover this demo's selected tab. To enable it to compare restored
   // _ButtonDemo objects with new ones, define hashCode and operator== .
 
+  @override
   bool operator==(Object other) {
     if (other.runtimeType != runtimeType)
       return false;
@@ -52,16 +53,19 @@ class _ButtonDemo {
     return typedOther.title == title && typedOther.text == text;
   }
 
+  @override
   int get hashCode => hashValues(title.hashCode, text.hashCode);
 }
 
 class ButtonsDemo extends StatefulWidget {
+  @override
   _ButtonsDemoState createState() => new _ButtonsDemoState();
 }
 
 class _ButtonsDemoState extends State<ButtonsDemo> {
   List<_ButtonDemo> demos;
 
+  @override
   void initState() {
     super.initState();
     demos = <_ButtonDemo>[
@@ -192,6 +196,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new TabBarSelection<_ButtonDemo>(
       values: demos,

examples/material_gallery/lib/demo/cards_demo.dart

@@ -43,6 +43,7 @@ class TravelDestinationItem extends StatelessWidget {
 
   final TravelDestination destination;
 
+  @override
   Widget build(BuildContext context) {
     ThemeData theme = Theme.of(context);
     TextStyle titleStyle = theme.textTheme.headline.copyWith(color: Colors.white);
@@ -115,6 +116,7 @@ class TravelDestinationItem extends StatelessWidget {
 }
 
 class CardsDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(

examples/material_gallery/lib/demo/chip_demo.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 
 class ChipDemo extends StatefulWidget {
+  @override
   _ChipDemoState createState() => new _ChipDemoState();
 }
 
@@ -17,6 +18,7 @@ class _ChipDemoState extends State<ChipDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> chips = <Widget>[
       new Chip(

examples/material_gallery/lib/demo/colors_demo.dart

@@ -54,6 +54,7 @@ class ColorItem extends StatelessWidget {
 
   String colorString() => "#${color.value.toRadixString(16).padLeft(8, '0').toUpperCase()}";
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       height: kColorItemHeight,
@@ -80,6 +81,7 @@ class ColorSwatchTabView extends StatelessWidget {
   final TextStyle blackTextStyle = Typography.black.body1;
   final TextStyle whiteTextStyle = Typography.white.body1;
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> colorItems =  swatch.colors.keys.map((int index) {
       return new DefaultTextStyle(
@@ -107,6 +109,7 @@ class ColorSwatchTabView extends StatelessWidget {
 }
 
 class ColorsDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new TabBarSelection<ColorSwatch>(
       values: colorSwatches,

examples/material_gallery/lib/demo/date_picker_demo.dart

@@ -8,6 +8,7 @@ import 'package:flutter/material.dart';
 import 'package:intl/intl.dart';
 
 class DatePickerDemo extends StatefulWidget {
+  @override
   _DatePickerDemoState createState() => new _DatePickerDemoState();
 }
 
@@ -28,6 +29,7 @@ class _DatePickerDemoState extends State<DatePickerDemo> {
     }
   }
 
+  @override
   Widget build(BuildContext context) {
     return
       new Scaffold(

examples/material_gallery/lib/demo/dialog_demo.dart

@@ -28,6 +28,7 @@ class DialogDemoItem extends StatelessWidget {
   final String text;
   final VoidCallback onPressed;
 
+  @override
   Widget build(BuildContext context) {
     return new InkWell(
       onTap: onPressed,
@@ -54,6 +55,7 @@ class DialogDemoItem extends StatelessWidget {
 }
 
 class DialogDemo extends StatefulWidget {
+  @override
   DialogDemoState createState() => new DialogDemoState();
 }
 
@@ -74,6 +76,7 @@ class DialogDemoState extends State<DialogDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final TextStyle dialogTextStyle = theme.textTheme.subhead.copyWith(color: theme.textTheme.caption.color);

examples/material_gallery/lib/demo/drop_down_demo.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 
 class DropDownDemo extends StatefulWidget {
+  @override
   _DropDownDemoState createState() => new _DropDownDemoState();
 }
 
@@ -18,6 +19,7 @@ class _DropDownDemoState extends State<DropDownDemo> {
     .toList();
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text("Dropdown Button")),

examples/material_gallery/lib/demo/fitness_demo.dart

@@ -16,6 +16,7 @@ SpriteSheet _sprites;
 class FitnessDemo extends StatelessWidget {
   FitnessDemo({ Key key }) : super(key: key);
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(
@@ -28,6 +29,8 @@ class FitnessDemo extends StatelessWidget {
 
 class _FitnessDemoContents extends StatefulWidget {
   _FitnessDemoContents({ Key key }) : super(key: key);
+
+  @override
   _FitnessDemoContentsState createState() => new _FitnessDemoContentsState();
 }
 
@@ -43,6 +46,7 @@ class _FitnessDemoContentsState extends State<_FitnessDemoContents> {
     _sprites = new SpriteSheet(_images['packages/flutter_gallery_assets/jumpingjack.png'], json);
   }
 
+  @override
   void initState() {
     super.initState();
 
@@ -73,6 +77,7 @@ class _FitnessDemoContentsState extends State<_FitnessDemoContents> {
 
   _WorkoutAnimationNode workoutAnimation;
 
+  @override
   Widget build(BuildContext context) {
     if (!assetsLoaded)
       return new Container();
@@ -248,6 +253,7 @@ class _WorkoutAnimationNode extends NodeWithSize {
     _jumpingJack.neutralPose();
   }
 
+  @override
   void update(double dt) {
     if (workingOut) {
       int millis = new DateTime.now().millisecondsSinceEpoch - _startTimeMillis;
@@ -273,6 +279,7 @@ class _ProgressCircle extends NodeWithSize {
 
   double value;
 
+  @override
   void paint(Canvas canvas) {
     applyTransformForPivot(canvas);
 
@@ -513,10 +520,12 @@ class _JumpingJackPart extends Sprite {
 class _Fireworks extends StatefulWidget {
   _Fireworks({ Key key }) : super(key: key);
 
+  @override
   _FireworksState createState() => new _FireworksState();
 }
 
 class _FireworksState extends State<_Fireworks> {
+  @override
   void initState() {
     super.initState();
     fireworks = new _FireworksNode();
@@ -524,6 +533,7 @@ class _FireworksState extends State<_Fireworks> {
 
   _FireworksNode fireworks;
 
+  @override
   Widget build(BuildContext context) {
     return new SpriteWidget(fireworks);
   }
@@ -533,6 +543,7 @@ class _FireworksNode extends NodeWithSize {
   _FireworksNode() : super(const Size(1024.0, 1024.0));
   double _countDown = 0.0;
 
+  @override
   void update(double dt) {
     if (_countDown <= 0.0) {
       _addExplosion();

examples/material_gallery/lib/demo/flexible_space_demo.dart

@@ -11,6 +11,7 @@ class _ContactCategory extends StatelessWidget {
   final IconData icon;
   final List<Widget> children;
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       padding: const EdgeInsets.symmetric(vertical: 16.0),
@@ -41,6 +42,7 @@ class _ContactItem extends StatelessWidget {
   final IconData icon;
   final List<String> lines;
 
+  @override
   Widget build(BuildContext context) {
     List<Widget> columnChildren = lines.sublist(0, lines.length - 1).map((String line) => new Text(line)).toList();
     columnChildren.add(new Text(lines.last, style: Theme.of(context).textTheme.caption));
@@ -68,6 +70,7 @@ class _ContactItem extends StatelessWidget {
 }
 
 class FlexibleSpaceDemo extends StatefulWidget {
+  @override
   FlexibleSpaceDemoState createState() => new FlexibleSpaceDemoState();
 }
 
@@ -77,6 +80,7 @@ class FlexibleSpaceDemoState extends State<FlexibleSpaceDemo> {
   final Key scrollableKey = new UniqueKey();
   AppBarBehavior _appBarBehavior = AppBarBehavior.scroll;
 
+  @override
   Widget build(BuildContext context) {
     return new Theme(
       data: new ThemeData(

examples/material_gallery/lib/demo/full_screen_dialog_demo.dart

@@ -27,6 +27,7 @@ class DateTimeItem extends StatelessWidget {
   final TimeOfDay time;
   final ValueChanged<DateTime> onChanged;
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
 
@@ -93,6 +94,7 @@ class DateTimeItem extends StatelessWidget {
 }
 
 class FullScreenDialogDemo extends StatefulWidget {
+  @override
   FullScreenDialogDemoState createState() => new FullScreenDialogDemoState();
 }
 
@@ -137,6 +139,7 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
 

examples/material_gallery/lib/demo/grid_list_demo.dart

@@ -55,6 +55,7 @@ class GridDemoPhotoItem extends StatelessWidget {
     ));
   }
 
+  @override
   Widget build(BuildContext context) {
     final Widget image = new GestureDetector(
       onTap: () { showPhoto(context); },
@@ -104,9 +105,12 @@ class GridListDemoGridDelegate extends FixedColumnCountGridDelegate {
     assert(tileHeightFactor != null && tileHeightFactor > 0.0);
   }
 
+  @override
   final int columnCount;
+
   final double tileHeightFactor;
 
+  @override
   GridSpecification getGridSpecification(BoxConstraints constraints, int childCount) {
     assert(constraints.maxWidth < double.INFINITY);
     assert(constraints.maxHeight < double.INFINITY);
@@ -121,6 +125,7 @@ class GridListDemoGridDelegate extends FixedColumnCountGridDelegate {
     );
   }
 
+  @override
   bool shouldRelayout(GridListDemoGridDelegate oldDelegate) {
     return columnCount != oldDelegate.columnCount
         || tileHeightFactor != oldDelegate.tileHeightFactor
@@ -131,6 +136,7 @@ class GridListDemoGridDelegate extends FixedColumnCountGridDelegate {
 class GridListDemo extends StatefulWidget {
   GridListDemo({ Key key }) : super(key: key);
 
+  @override
   GridListDemoState createState() => new GridListDemoState();
 }
 
@@ -169,6 +175,7 @@ class GridListDemoState extends State<GridListDemo> {
   // When the ScrollableGrid first appears we want the last row to only be
   // partially visible, to help the user recognize that the grid is scrollable.
   // The GridListDemoGridDelegate's tileHeightFactor is used for this.
+  @override
   Widget build(BuildContext context) {
     final Orientation orientation = MediaQuery.of(context).orientation;
     return new Scaffold(

examples/material_gallery/lib/demo/icons_demo.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 
 class IconsDemo extends StatefulWidget {
+  @override
   IconsDemoState createState() => new IconsDemoState();
 }
 
@@ -61,6 +62,7 @@ class IconsDemoState extends State<IconsDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final TextStyle textStyle = theme.textTheme.subhead.copyWith(color: theme.textTheme.caption.color);

examples/material_gallery/lib/demo/leave_behind_demo.dart

@@ -28,6 +28,7 @@ class LeaveBehindItem {
 class LeaveBehindDemo extends StatefulWidget {
   LeaveBehindDemo({ Key key }) : super(key: key);
 
+  @override
   LeaveBehindDemoState createState() => new LeaveBehindDemoState();
 }
 
@@ -47,6 +48,7 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
     });
   }
 
+  @override
   void initState() {
     super.initState();
     initListItems();
@@ -122,6 +124,7 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       key: _scaffoldKey,

examples/material_gallery/lib/demo/list_demo.dart

@@ -13,6 +13,7 @@ enum ListDemoItemSize {
 class ListDemo extends StatefulWidget {
   ListDemo({ Key key }) : super(key: key);
 
+  @override
   ListDemoState createState() => new ListDemoState();
 }
 
@@ -153,6 +154,7 @@ class ListDemoState extends State<ListDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     final String layoutText = _dense ? " \u2013 Dense" : "";
     String  itemSizeText;

examples/material_gallery/lib/demo/menu_demo.dart

@@ -7,6 +7,7 @@ import 'package:flutter/material.dart';
 class MenuDemo extends StatefulWidget {
   MenuDemo({ Key key }) : super(key: key);
 
+  @override
   MenuDemoState createState() => new MenuDemoState();
 }
 
@@ -24,6 +25,7 @@ class MenuDemoState extends State<MenuDemo> {
   final String _checkedValue4 = 'Four';
   List<String> _checkedValues;
 
+  @override
   void initState() {
     super.initState();
     _simpleValue = _simpleValue2;
@@ -53,6 +55,7 @@ class MenuDemoState extends State<MenuDemo> {
 
   bool isChecked(String value) => _checkedValues.contains(value);
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       key: _scaffoldKey,

examples/material_gallery/lib/demo/modal_bottom_sheet_demo.dart

@@ -11,6 +11,7 @@ class ModalBottomSheetDemo extends StatelessWidget {
     textAlign: TextAlign.center
   );
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text("Modal Bottom Sheet")),

examples/material_gallery/lib/demo/page_selector_demo.dart

@@ -12,6 +12,7 @@ class PageSelectorDemo extends StatelessWidget {
       selection.value = selection.values[(selection.index + delta).clamp(0, selection.values.length - 1)];
   }
 
+  @override
   Widget build(BuildContext notUsed) { // Can't find the TabBarSelection from this context.
     final List<IconData> icons = <IconData>[
       Icons.event,

examples/material_gallery/lib/demo/persistent_bottom_sheet_demo.dart

@@ -26,6 +26,7 @@ class PersistentBottomSheetDemo extends StatelessWidget {
     });
   }
 
+  @override
   Widget build(BuildContext notUsed) { // Can't find the Scaffold from this context.
     return new Scaffold(
       appBar: new AppBar(title: new Text("Persistent Bottom Sheet")),

examples/material_gallery/lib/demo/progress_indicator_demo.dart

@@ -5,11 +5,13 @@
 import 'package:flutter/material.dart';
 
 class ProgressIndicatorDemo extends StatefulWidget {
+  @override
   _ProgressIndicatorDemoState createState() => new _ProgressIndicatorDemoState();
 }
 
 class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo> {
 
+  @override
   void initState() {
     super.initState();
     controller = new AnimationController(
@@ -81,6 +83,7 @@ class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text('Progress Indicators')),

examples/material_gallery/lib/demo/scrolling_techniques_demo.dart

@@ -19,6 +19,7 @@ class _BarGraphic extends StatelessWidget {
   final String leftText;
   final String rightText;
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       height: height,
@@ -85,6 +86,7 @@ class _TechniqueItem extends StatelessWidget {
     Navigator.push(context, new MaterialPageRoute<Null>(builder: builder));
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Card(
       child: new InkWell(
@@ -111,6 +113,7 @@ const String _introText =
   "specified it is stacked on top of the ToolBar.";
 
 class ScrollingTechniquesDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text('Scrolling Techniques')),

examples/material_gallery/lib/demo/slider_demo.dart

@@ -5,12 +5,14 @@
 import 'package:flutter/material.dart';
 
 class SliderDemo extends StatefulWidget {
+  @override
   _SliderDemoState createState() => new _SliderDemoState();
 }
 
 class _SliderDemoState extends State<SliderDemo> {
   double _value = 25.0;
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text("Sliders")),

examples/material_gallery/lib/demo/snack_bar_demo.dart

@@ -56,6 +56,7 @@ class SnackBarDemo extends StatelessWidget {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(

examples/material_gallery/lib/demo/tabs_demo.dart

@@ -23,6 +23,7 @@ class TabsDemo extends StatelessWidget {
     Icons.language: 'LANGUAGE',
   };
 
+  @override
   Widget build(BuildContext context) {
     final Color iconColor = Theme.of(context).accentColor;
     return new TabBarSelection<IconData>(

examples/material_gallery/lib/demo/tabs_fab_demo.dart

@@ -26,6 +26,7 @@ const String _explanatoryText =
   "by its key.";
 
 class TabsFabDemo extends StatefulWidget {
+  @override
   _TabsFabDemoState createState() => new _TabsFabDemoState();
 }
 
@@ -41,6 +42,7 @@ class _TabsFabDemoState extends State<TabsFabDemo> {
   ];
   _Page selectedPage;
 
+  @override
   void initState() {
     super.initState();
     selectedPage = pages[0];
@@ -88,6 +90,7 @@ class _TabsFabDemoState extends State<TabsFabDemo> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new TabBarSelection<_Page>(
       values: pages,

examples/material_gallery/lib/demo/text_field_demo.dart

@@ -7,6 +7,7 @@ import 'package:flutter/material.dart';
 class TextFieldDemo extends StatefulWidget {
   TextFieldDemo({ Key key }) : super(key: key);
 
+  @override
   TextFieldDemoState createState() => new TextFieldDemoState();
 }
 
@@ -59,6 +60,7 @@ class TextFieldDemoState extends State<TextFieldDemo> {
     return null;
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       key: _scaffoldKey,

examples/material_gallery/lib/demo/time_picker_demo.dart

@@ -7,6 +7,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 
 class TimePickerDemo extends StatefulWidget {
+  @override
   _TimePickerDemoState createState() => new _TimePickerDemoState();
 }
 
@@ -25,6 +26,7 @@ class _TimePickerDemoState extends State<TimePickerDemo> {
     }
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text("Time Picker")),

examples/material_gallery/lib/demo/toggle_controls_demo.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 
 class ToggleControlsDemo extends StatefulWidget {
+  @override
   _ToggleControlsDemoState createState() => new _ToggleControlsDemoState();
 }
 
@@ -31,6 +32,7 @@ class _ToggleControlsDemoState extends State<ToggleControlsDemo> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text("Selection Controls")),

examples/material_gallery/lib/demo/tooltip_demo.dart

@@ -10,6 +10,7 @@ const String _introText =
   "apps accessible, like screen readers.";
 
 class TooltipDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     return new Scaffold(

examples/material_gallery/lib/demo/two_level_list_demo.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 
 class TwoLevelListDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(title: new Text('Expand/Collapse List Control')),

examples/material_gallery/lib/demo/typography_demo.dart

@@ -16,6 +16,7 @@ class TextStyleItem extends StatelessWidget {
   final TextStyle style;
   final String text;
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final TextStyle nameStyle = theme.textTheme.body1.copyWith(color: theme.textTheme.caption.color);
@@ -38,6 +39,7 @@ class TextStyleItem extends StatelessWidget {
 }
 
 class TypographyDemo extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     final TextTheme textTheme = Theme.of(context).textTheme;
     final List<Widget> styleItems = <Widget>[

examples/material_gallery/lib/demo/weather_demo.dart

@@ -19,6 +19,8 @@ enum WeatherType {
 
 class WeatherDemo extends StatefulWidget {
   WeatherDemo({ Key key }) : super(key: key);
+
+  @override
   _WeatherDemoState createState() => new _WeatherDemoState();
 }
 
@@ -42,6 +44,7 @@ class _WeatherDemoState extends State<WeatherDemo> {
     _sprites = new SpriteSheet(_images['packages/flutter_gallery_assets/weathersprites.png'], json);
   }
 
+  @override
   void initState() {
     super.initState();
 
@@ -58,6 +61,7 @@ class _WeatherDemoState extends State<WeatherDemo> {
 
   WeatherWorld weatherWorld;
 
+  @override
   Widget build(BuildContext context) {
     if (!assetsLoaded) {
       return new Scaffold(
@@ -132,6 +136,7 @@ class WeatherButton extends StatelessWidget {
   final bool selected;
   final VoidCallback onPressed;
 
+  @override
   Widget build(BuildContext context) {
     Color color;
     if (selected)
@@ -262,6 +267,7 @@ class WeatherWorld extends NodeWithSize {
     _snow.active = weatherType == WeatherType.snow;
   }
 
+  @override
   void spriteBoxPerformedLayout() {
     _sun.position = spriteBox.visibleArea.topLeft + const Offset(350.0, 180.0);
   }
@@ -273,6 +279,7 @@ class GradientNode extends NodeWithSize {
   Color colorTop;
   Color colorBottom;
 
+  @override
   void paint(Canvas canvas) {
     applyTransformForPivot(canvas);
 
@@ -426,6 +433,7 @@ class Ray extends Sprite {
     ));
   }
 
+  @override
   void update(double dt) {
     rotation += dt * _rotationSpeed;
   }

examples/material_gallery/lib/gallery/app.dart

@@ -11,6 +11,7 @@ class GalleryApp extends StatefulWidget {
 
   static GalleryAppState of(BuildContext context) => context.ancestorStateOfType(const TypeMatcher<GalleryAppState>());
 
+  @override
   GalleryAppState createState() => new GalleryAppState();
 }
 
@@ -23,6 +24,7 @@ class GalleryAppState extends State<GalleryApp> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new MaterialApp(
       title: 'Flutter Material Gallery',

examples/material_gallery/lib/gallery/drawer.dart

@@ -21,6 +21,7 @@ class GalleryDrawer extends StatelessWidget {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Drawer(
       child: new Block(

examples/material_gallery/lib/gallery/home.dart

@@ -42,10 +42,12 @@ import '../demo/weather_demo.dart';
 class GalleryHome extends StatefulWidget {
   GalleryHome({ Key key }) : super(key: key);
 
+  @override
   GalleryHomeState createState() => new GalleryHomeState();
 }
 
 class GalleryHomeState extends State<GalleryHome> {
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBarHeight: 128.0,

examples/material_gallery/lib/gallery/section.dart

@@ -61,6 +61,7 @@ class GallerySection extends StatelessWidget {
     ));
   }
 
+  @override
   Widget build (BuildContext context) {
     final ThemeData theme = new ThemeData(
       brightness: Theme.of(context).brightness,

examples/stocks/lib/main.dart

@@ -24,6 +24,7 @@ import 'stock_symbol_viewer.dart';
 import 'stock_types.dart';
 
 class StocksApp extends StatefulWidget {
+  @override
   StocksAppState createState() => new StocksAppState();
 }
 
@@ -45,6 +46,7 @@ class StocksAppState extends State<StocksApp> {
     showSemanticsDebugger: false
   );
 
+  @override
   void initState() {
     super.initState();
     new StockDataFetcher((StockData data) {
@@ -99,6 +101,7 @@ class StocksAppState extends State<StocksApp> {
     return StockStrings.instance;
   }
 
+  @override
   Widget build(BuildContext context) {
     assert(() {
       debugPaintSizeEnabled = _configuration.debugShowSizes;

examples/stocks/lib/stock_arrow.dart

@@ -12,6 +12,7 @@ class StockArrowPainter extends CustomPainter {
   final Color color;
   final double percentChange;
 
+  @override
   void paint(Canvas canvas, Size size) {
     Paint paint = new Paint()..color = color;
     paint.strokeWidth = 1.0;
@@ -44,6 +45,7 @@ class StockArrowPainter extends CustomPainter {
     canvas.drawCircle(new Point(centerX, centerY), r, paint);
   }
 
+  @override
   bool shouldRepaint(StockArrowPainter oldPainter) {
     return oldPainter.color != color
         || oldPainter.percentChange != percentChange;
@@ -67,6 +69,7 @@ class StockArrow extends StatelessWidget {
     return Colors.red[_colorIndexForPercentChange(percentChange)];
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       width: 40.0,

examples/stocks/lib/stock_home.dart

@@ -19,6 +19,7 @@ enum _StockMenuItem { autorefresh, refresh, speedUp, speedDown }
 enum StockHomeTab { market, portfolio }
 
 class _NotImplementedDialog extends StatelessWidget {
+  @override
   Widget build(BuildContext context) {
     return new Dialog(
       title: new Text('Not Implemented'),
@@ -58,6 +59,7 @@ class StockHome extends StatefulWidget {
   final StockConfiguration configuration;
   final ValueChanged<StockConfiguration> updater;
 
+  @override
   StockHomeState createState() => new StockHomeState();
 }
 
@@ -336,6 +338,7 @@ class StockHomeState extends State<StockHome> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new TabBarSelection<StockHomeTab>(
       values: <StockHomeTab>[StockHomeTab.market, StockHomeTab.portfolio],
@@ -356,6 +359,7 @@ class StockHomeState extends State<StockHome> {
 }
 
 class _CreateCompanySheet extends StatefulWidget {
+  @override
   _CreateCompanySheetState createState() => new _CreateCompanySheetState();
 }
 
@@ -368,6 +372,7 @@ class _CreateCompanySheetState extends State<_CreateCompanySheet> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     // TODO(ianh): Fill this out.
     return new Column(

examples/stocks/lib/stock_list.dart

@@ -16,6 +16,7 @@ class StockList extends StatelessWidget {
   final StockRowActionCallback onShow;
   final StockRowActionCallback onAction;
 
+  @override
   Widget build(BuildContext context) {
     return new ScrollableList(
       key: const ValueKey<String>('stock-list'),

examples/stocks/lib/stock_row.dart

@@ -11,9 +11,12 @@ enum StockRowPartKind { arrow }
 
 class StockRowPartKey extends Key {
   const StockRowPartKey(this.keySalt, this.stock, this.part) : super.constructor();
+
   final Object keySalt;
   final Stock stock;
   final StockRowPartKind part;
+
+  @override
   bool operator ==(dynamic other) {
     if (identical(this, other))
       return true;
@@ -24,7 +27,11 @@ class StockRowPartKey extends Key {
         && stock == typedOther.stock
         && part == typedOther.part;
   }
+
+  @override
   int get hashCode => hashValues(keySalt, stock, part);
+
+  @override
   String toString() => '[$runtimeType ${keySalt.toString().split(".")[1]}:${stock.symbol}:${part.toString().split(".")[1]}]';
 }
 
@@ -54,6 +61,7 @@ class StockRow extends StatelessWidget {
     return callback == null ? null : () => callback(stock, _arrowKey);
   }
 
+  @override
   Widget build(BuildContext context) {
     final String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";
     String changeInPrice = "${stock.percentChange.toStringAsFixed(2)}%";

examples/stocks/lib/stock_settings.dart

@@ -12,6 +12,7 @@ class StockSettings extends StatefulWidget {
   final StockConfiguration configuration;
   final ValueChanged<StockConfiguration> updater;
 
+  @override
   StockSettingsState createState() => new StockSettingsState();
 }
 
@@ -245,6 +246,7 @@ class StockSettingsState extends State<StockSettings> {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: buildAppBar(context),

examples/stocks/lib/stock_symbol_viewer.dart

@@ -13,6 +13,7 @@ class StockSymbolView extends StatelessWidget {
 
   final Stock stock;
 
+  @override
   Widget build(BuildContext context) {
     String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";
     String changeInPrice = "${stock.percentChange.toStringAsFixed(2)}%";
@@ -71,6 +72,7 @@ class StockSymbolPage extends StatelessWidget {
 
   final Stock stock;
 
+  @override
   Widget build(BuildContext context) {
     return new Scaffold(
       appBar: new AppBar(
@@ -93,6 +95,7 @@ class StockSymbolBottomSheet extends StatelessWidget {
 
   final Stock stock;
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       padding: new EdgeInsets.all(10.0),

packages/cassowary/lib/expression.dart

@@ -153,6 +153,7 @@ class Expression extends _EquationMember {
     return null;
   }
 
+  @override
   _EquationMember operator *(_EquationMember m) {
     _Pair<Expression, double> args = _findMulitplierAndMultiplicand(m);
 
@@ -166,6 +167,7 @@ class Expression extends _EquationMember {
     return args.first._applyMultiplicand(args.second);
   }
 
+  @override
   _EquationMember operator /(_EquationMember m) {
     if (!m.isConstant) {
       throw new ParserException(
@@ -176,6 +178,7 @@ class Expression extends _EquationMember {
     return this._applyMultiplicand(1.0 / m.value);
   }
 
+  @override
   String toString() {
     StringBuffer buffer = new StringBuffer();
 

packages/cassowary/lib/param.dart

@@ -18,12 +18,15 @@ class Param extends _EquationMember {
 
   dynamic context;
 
+  @override
   bool get isConstant => false;
 
+  @override
   double get value => variable.value;
 
   String get name => variable.name;
   void set name(String name) { variable.name = name; }
 
+  @override
   Expression asExpression() => new Expression(<Term>[new Term(variable, 1.0)], 0.0);
 }

packages/cassowary/lib/parser_exception.dart

@@ -9,6 +9,7 @@ class ParserException implements Exception {
   List<_EquationMember> members;
   ParserException(this.message, this.members);
 
+  @override
   String toString() {
     if (message == null) return "Error while parsing constraint or expression";
     return "Error: '$message' while trying to parse constraint or expression";

packages/cassowary/lib/row.dart

@@ -65,6 +65,7 @@ class _Row {
     insertRow(row, coefficient);
   }
 
+  @override
   String toString() {
     StringBuffer buffer = new StringBuffer();
 

packages/cassowary/lib/solver.dart

@@ -588,6 +588,7 @@ class Solver {
     return entering ?? new _Symbol(_SymbolType.invalid, 0);
   }
 
+  @override
   String toString() {
     StringBuffer buffer = new StringBuffer();
     String separator = "\n~~~~~~~~~";

packages/cassowary/lib/symbol.dart

@@ -12,6 +12,7 @@ class _Symbol {
 
   _Symbol(this.type, this.tick);
 
+  @override
   String toString() {
     String typeString = 'unknown';
     switch (type) {

packages/cassowary/lib/term.dart

@@ -10,13 +10,17 @@ class Term extends _EquationMember {
   final Variable variable;
   final double coefficient;
 
+  @override
   bool get isConstant => false;
 
+  @override
   double get value => coefficient * variable.value;
 
+  @override
   Expression asExpression() =>
       new Expression([new Term(this.variable, this.coefficient)], 0.0);
 
+  @override
   String toString() {
     StringBuffer buffer = new StringBuffer();
 

packages/flutter/lib/src/animation/animation.dart

@@ -62,6 +62,7 @@ abstract class Animation<T> {
   /// Whether this animation is stopped at the end.
   bool get isCompleted => status == AnimationStatus.completed;
 
+  @override
   String toString() {
     return '$runtimeType(${toStringDetails()})';
   }

packages/flutter/lib/src/animation/animation_controller.dart

@@ -99,6 +99,7 @@ class AnimationController extends Animation<double>
   /// Setting this value also stops the controller if it is currently
   /// running; if this happens, it also notifies all the status
   /// listeners.
+  @override
   double get value => _value;
   double _value;
   void set value(double newValue) {
@@ -114,6 +115,7 @@ class AnimationController extends Animation<double>
 
   _AnimationDirection _direction;
 
+  @override
   AnimationStatus get status {
     if (!isAnimating && value == upperBound)
       return AnimationStatus.completed;
@@ -202,6 +204,7 @@ class AnimationController extends Animation<double>
   }
 
   /// Stops running this animation.
+  @override
   void dispose() {
     stop();
   }
@@ -224,6 +227,7 @@ class AnimationController extends Animation<double>
     _checkStatusChanged();
   }
 
+  @override
   String toStringDetails() {
     String paused = isAnimating ? '' : '; paused';
     String label = debugLabel == null ? '' : '; for $debugLabel';
@@ -245,6 +249,7 @@ class _InterpolationSimulation extends Simulation {
   final double _end;
   final Curve _curve;
 
+  @override
   double x(double timeInSeconds) {
     assert(timeInSeconds >= 0.0);
     double t = (timeInSeconds / _durationInSeconds).clamp(0.0, 1.0);
@@ -256,8 +261,10 @@ class _InterpolationSimulation extends Simulation {
       return _begin + (_end - _begin) * _curve.transform(t);
   }
 
+  @override
   double dx(double timeInSeconds) => 1.0;
 
+  @override
   bool isDone(double timeInSeconds) => timeInSeconds > _durationInSeconds;
 }
 
@@ -272,13 +279,16 @@ class _RepeatingSimulation extends Simulation {
 
   final double _periodInSeconds;
 
+  @override
   double x(double timeInSeconds) {
     assert(timeInSeconds >= 0.0);
     final double t = (timeInSeconds / _periodInSeconds) % 1.0;
     return ui.lerpDouble(min, max, t);
   }
 
+  @override
   double dx(double timeInSeconds) => 1.0;
 
+  @override
   bool isDone(double timeInSeconds) => false;
 }

packages/flutter/lib/src/animation/animations.dart

@@ -11,11 +11,22 @@ import 'listener_helpers.dart';
 class _AlwaysCompleteAnimation extends Animation<double> {
   const _AlwaysCompleteAnimation();
 
+  @override
   void addListener(VoidCallback listener) { }
+
+  @override
   void removeListener(VoidCallback listener) { }
+
+  @override
   void addStatusListener(AnimationStatusListener listener) { }
+
+  @override
   void removeStatusListener(AnimationStatusListener listener) { }
+
+  @override
   AnimationStatus get status => AnimationStatus.completed;
+
+  @override
   double get value => 1.0;
 }
 
@@ -29,11 +40,22 @@ const Animation<double> kAlwaysCompleteAnimation = const _AlwaysCompleteAnimatio
 class _AlwaysDismissedAnimation extends Animation<double> {
   const _AlwaysDismissedAnimation();
 
+  @override
   void addListener(VoidCallback listener) { }
+
+  @override
   void removeListener(VoidCallback listener) { }
+
+  @override
   void addStatusListener(AnimationStatusListener listener) { }
+
+  @override
   void removeStatusListener(AnimationStatusListener listener) { }
+
+  @override
   AnimationStatus get status => AnimationStatus.dismissed;
+
+  @override
   double get value => 0.0;
 }
 
@@ -48,12 +70,22 @@ const Animation<double> kAlwaysDismissedAnimation = const _AlwaysDismissedAnimat
 class AlwaysStoppedAnimation<T> extends Animation<T> {
   const AlwaysStoppedAnimation(this.value);
 
+  @override
   final T value;
 
+  @override
   void addListener(VoidCallback listener) { }
+
+  @override
   void removeListener(VoidCallback listener) { }
+
+  @override
   void addStatusListener(AnimationStatusListener listener) { }
+
+  @override
   void removeStatusListener(AnimationStatusListener listener) { }
+
+  @override
   AnimationStatus get status => AnimationStatus.forward;
 }
 
@@ -123,6 +155,7 @@ class ProxyAnimation extends Animation<double>
     }
   }
 
+  @override
   void didStartListening() {
     if (_parent != null) {
       _parent.addListener(notifyListeners);
@@ -130,6 +163,7 @@ class ProxyAnimation extends Animation<double>
     }
   }
 
+  @override
   void didStopListening() {
     if (_parent != null) {
       _parent.removeListener(notifyListeners);
@@ -137,7 +171,10 @@ class ProxyAnimation extends Animation<double>
     }
   }
 
+  @override
   AnimationStatus get status => _parent != null ? _parent.status : _status;
+
+  @override
   double get value => _parent != null ? _parent.value : _value;
 }
 
@@ -155,19 +192,24 @@ class ReverseAnimation extends Animation<double>
   /// The animation whose value and direction this animation is reversing.
   final Animation<double> parent;
 
+  @override
   void addListener(VoidCallback listener) {
     didRegisterListener();
     parent.addListener(listener);
   }
+
+  @override
   void removeListener(VoidCallback listener) {
     parent.removeListener(listener);
     didUnregisterListener();
   }
 
+  @override
   void didStartListening() {
     parent.addStatusListener(_statusChangeHandler);
   }
 
+  @override
   void didStopListening() {
     parent.removeStatusListener(_statusChangeHandler);
   }
@@ -176,7 +218,10 @@ class ReverseAnimation extends Animation<double>
     notifyStatusListeners(_reverseStatus(status));
   }
 
+  @override
   AnimationStatus get status => _reverseStatus(parent.status);
+
+  @override
   double get value => 1.0 - parent.value;
 
   AnimationStatus _reverseStatus(AnimationStatus status) {
@@ -206,6 +251,7 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
   }
 
   /// The animation to which this animation applies a curve.
+  @override
   final Animation<double> parent;
 
   /// The curve to use in the forward direction.
@@ -238,6 +284,7 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
     }
   }
 
+  @override
   double get value {
     final bool useForwardCurve = reverseCurve == null || (_curveDirection ?? parent.status) != AnimationStatus.reverse;
     Curve activeCurve = useForwardCurve ? curve : reverseCurve;
@@ -306,6 +353,7 @@ class TrainHoppingAnimation extends Animation<double>
     assert(_lastStatus != null);
   }
 
+  @override
   AnimationStatus get status => _currentTrain.status;
 
   double _lastValue;
@@ -342,10 +390,12 @@ class TrainHoppingAnimation extends Animation<double>
       onSwitchedTrain();
   }
 
+  @override
   double get value => _currentTrain.value;
 
   /// Frees all the resources used by this performance.
   /// After this is called, this object is no longer usable.
+  @override
   void dispose() {
     assert(_currentTrain != null);
     _currentTrain.removeStatusListener(_statusChangeHandler);

packages/flutter/lib/src/animation/curves.dart

@@ -31,13 +31,18 @@ abstract class Curve {
 /// The identity map over the unit interval.
 class Linear extends Curve {
   const Linear();
+
+  @override
   double transform(double t) => t;
 }
 
 /// A sawtooth curve that repeats a given number of times over the unit interval.
 class SawTooth extends Curve {
   const SawTooth(this.count);
+
   final int count;
+
+  @override
   double transform(double t) {
     t *= count;
     return t - t.truncateToDouble();
@@ -57,6 +62,7 @@ class Interval extends Curve {
   /// The curve to apply between [start] and [end].
   final Curve curve;
 
+  @override
   double transform(double t) {
     assert(start >= 0.0);
     assert(start <= 1.0);
@@ -79,6 +85,7 @@ class Cubic extends Curve {
   final double c;
   final double d;
 
+  @override
   double transform(double t) {
     double start = 0.0;
     double end = 1.0;
@@ -112,13 +119,18 @@ double _bounce(double t) {
 /// A curve that is the reversed inversion of its given curve.
 class FlippedCurve extends Curve {
   FlippedCurve(this.curve);
+
   final Curve curve;
+
+  @override
   double transform(double t) => 1.0 - curve.transform(1.0 - t);
 }
 
 /// An oscillating curve that grows in magnitude.
 class BounceInCurve extends Curve {
   const BounceInCurve();
+
+  @override
   double transform(double t) {
     return 1.0 - _bounce(1.0 - t);
   }
@@ -127,6 +139,8 @@ class BounceInCurve extends Curve {
 /// An oscillating curve that shrink in magnitude.
 class BounceOutCurve extends Curve {
   const BounceOutCurve();
+
+  @override
   double transform(double t) {
     return _bounce(t);
   }
@@ -135,6 +149,8 @@ class BounceOutCurve extends Curve {
 /// An oscillating curve that first grows and then shrink in magnitude.
 class BounceInOutCurve extends Curve {
   const BounceInOutCurve();
+
+  @override
   double transform(double t) {
     if (t < 0.5)
       return (1.0 - _bounce(1.0 - t)) * 0.5;
@@ -146,7 +162,10 @@ class BounceInOutCurve extends Curve {
 /// An oscillating curve that grows in magnitude while overshooting its bounds.
 class ElasticInCurve extends Curve {
   const ElasticInCurve([this.period = 0.4]);
+
   final double period;
+
+  @override
   double transform(double t) {
     double s = period / 4.0;
     t = t - 1.0;
@@ -157,7 +176,10 @@ class ElasticInCurve extends Curve {
 /// An oscillating curve that shrinks in magnitude while overshooting its bounds.
 class ElasticOutCurve extends Curve {
   const ElasticOutCurve([this.period = 0.4]);
+
   final double period;
+
+  @override
   double transform(double t) {
     double s = period / 4.0;
     return math.pow(2.0, -10 * t) * math.sin((t - s) * (math.PI * 2.0) / period) + 1.0;
@@ -167,7 +189,10 @@ class ElasticOutCurve extends Curve {
 /// An oscillating curve that grows and then shrinks in magnitude while overshooting its bounds.
 class ElasticInOutCurve extends Curve {
   const ElasticInOutCurve([this.period = 0.4]);
+
   final double period;
+
+  @override
   double transform(double t) {
     double s = period / 4.0;
     t = 2.0 * t - 1.0;

packages/flutter/lib/src/animation/forces.dart

@@ -37,6 +37,7 @@ class SpringForce extends Force {
     distance: 0.01
   );
 
+  @override
   Simulation release(double position, double velocity) {
     double target = velocity < 0.0 ? this.left - tolerance.distance
                                    : this.right + tolerance.distance;

packages/flutter/lib/src/animation/listener_helpers.dart

@@ -14,18 +14,23 @@ abstract class _ListenerMixin {
 /// A mixin that helps listen to another object only when this object has registered listeners.
 abstract class AnimationLazyListenerMixin implements _ListenerMixin {
   int _listenerCounter = 0;
+
+  @override
   void didRegisterListener() {
     assert(_listenerCounter >= 0);
     if (_listenerCounter == 0)
       didStartListening();
     _listenerCounter += 1;
   }
+
+  @override
   void didUnregisterListener() {
     assert(_listenerCounter >= 1);
     _listenerCounter -= 1;
     if (_listenerCounter == 0)
       didStopListening();
   }
+
   void didStartListening();
   void didStopListening();
   bool get isListening => _listenerCounter > 0;
@@ -34,7 +39,10 @@ abstract class AnimationLazyListenerMixin implements _ListenerMixin {
 /// A mixin that replaces the didRegisterListener/didUnregisterListener contract
 /// with a dispose contract.
 abstract class AnimationEagerListenerMixin implements _ListenerMixin {
+  @override
   void didRegisterListener() { }
+
+  @override
   void didUnregisterListener() { }
 
   /// Release any resources used by this object.

packages/flutter/lib/src/animation/tween.dart

@@ -32,10 +32,12 @@ class _AnimatedEvaluation<T> extends Animation<T> with AnimationWithParentMixin<
   _AnimatedEvaluation(this.parent, this._evaluatable);
 
   /// The animation from which this value is derived.
+  @override
   final Animation<double> parent;
 
   final Animatable<T> _evaluatable;
 
+  @override
   T get value => _evaluatable.evaluate(parent);
 }
 
@@ -45,6 +47,7 @@ class _ChainedEvaluation<T> extends Animatable<T> {
   final Animatable<double> _parent;
   final Animatable<T> _evaluatable;
 
+  @override
   T evaluate(Animation<double> animation) {
     double value = _parent.evaluate(animation);
     return _evaluatable.evaluate(new AlwaysStoppedAnimation<double>(value));
@@ -65,6 +68,7 @@ class Tween<T extends dynamic> extends Animatable<T> {
   T lerp(double t) => begin + (end - begin) * t;
 
   /// Returns the interpolated value for the current value of the given animation.
+  @override
   T evaluate(Animation<double> animation) {
     if (end == null)
       return begin;
@@ -76,6 +80,7 @@ class Tween<T extends dynamic> extends Animatable<T> {
     return lerp(t);
   }
 
+  @override
   String toString() => '$runtimeType($begin \u2192 $end)';
 }
 
@@ -86,6 +91,7 @@ class Tween<T extends dynamic> extends Animatable<T> {
 class ColorTween extends Tween<Color> {
   ColorTween({ Color begin, Color end }) : super(begin: begin, end: end);
 
+  @override
   Color lerp(double t) => Color.lerp(begin, end, t);
 }
 
@@ -96,6 +102,7 @@ class ColorTween extends Tween<Color> {
 class SizeTween extends Tween<Size> {
   SizeTween({ Size begin, Size end }) : super(begin: begin, end: end);
 
+  @override
   Size lerp(double t) => Size.lerp(begin, end, t);
 }
 
@@ -106,6 +113,7 @@ class SizeTween extends Tween<Size> {
 class RectTween extends Tween<Rect> {
   RectTween({ Rect begin, Rect end }) : super(begin: begin, end: end);
 
+  @override
   Rect lerp(double t) => Rect.lerp(begin, end, t);
 }
 
@@ -123,6 +131,7 @@ class IntTween extends Tween<int> {
 
   // The inherited lerp() function doesn't work with ints because it multiplies
   // the begin and end types by a double, and int * double returns a double.
+  @override
   int lerp(double t) => (begin + (end - begin) * t).round();
 }
 
@@ -140,6 +149,7 @@ class StepTween extends Tween<int> {
 
   // The inherited lerp() function doesn't work with ints because it multiplies
   // the begin and end types by a double, and int * double returns a double.
+  @override
   int lerp(double t) => (begin + (end - begin) * t).floor();
 }
 
@@ -154,6 +164,7 @@ class CurveTween extends Animatable<double> {
   /// The curve to use when transforming the value of the animation.
   Curve curve;
 
+  @override
   double evaluate(Animation<double> animation) {
     double t = animation.value;
     if (t == 0.0 || t == 1.0) {

packages/flutter/lib/src/gestures/binding.dart

@@ -21,6 +21,7 @@ typedef void GesturerExceptionHandler(PointerEvent event, HitTestTarget target,
 /// A binding for the gesture subsystem.
 abstract class Gesturer extends BindingBase implements HitTestTarget, HitTestable {
 
+  @override
   void initInstances() {
     super.initInstances();
     _instance = this;
@@ -76,6 +77,7 @@ abstract class Gesturer extends BindingBase implements HitTestTarget, HitTestabl
   }
 
   /// Determine which [HitTestTarget] objects are located at a given position.
+  @override
   void hitTest(HitTestResult result, Point position) {
     result.add(new HitTestEntry(this));
   }
@@ -113,6 +115,7 @@ abstract class Gesturer extends BindingBase implements HitTestTarget, HitTestabl
     }
   }
 
+  @override
   void handleEvent(PointerEvent event, HitTestEntry entry) {
     pointerRouter.route(event);
     if (event is PointerDownEvent) {

packages/flutter/lib/src/gestures/drag.dart

@@ -46,6 +46,7 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
 
   Map<int, VelocityTracker> _velocityTrackers = new Map<int, VelocityTracker>();
 
+  @override
   void addPointer(PointerEvent event) {
     startTrackingPointer(event.pointer);
     _velocityTrackers[event.pointer] = new VelocityTracker();
@@ -56,6 +57,7 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
     }
   }
 
+  @override
   void handleEvent(PointerEvent event) {
     assert(_state != DragState.ready);
     if (event is PointerMoveEvent) {
@@ -75,6 +77,7 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
     stopTrackingIfPointerNoLongerDown(event);
   }
 
+  @override
   void acceptGesture(int pointer) {
     if (_state != DragState.accepted) {
       _state = DragState.accepted;
@@ -87,6 +90,7 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
     }
   }
 
+  @override
   void didStopTrackingLastPointer(int pointer) {
     if (_state == DragState.possible) {
       resolve(GestureDisposition.rejected);
@@ -108,6 +112,7 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
     _velocityTrackers.clear();
   }
 
+  @override
   void dispose() {
     _velocityTrackers.clear();
     super.dispose();
@@ -115,27 +120,45 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends OneSequenceGest
 }
 
 class VerticalDragGestureRecognizer extends _DragGestureRecognizer<double> {
+  @override
   double get _initialPendingDragDelta => 0.0;
+
+  @override
   double _getDragDelta(PointerEvent event) => event.delta.dy;
+
+  @override
   bool get _hasSufficientPendingDragDeltaToAccept => _pendingDragDelta.abs() > kTouchSlop;
 
+  @override
   String toStringShort() => 'vertical drag';
 }
 
 class HorizontalDragGestureRecognizer extends _DragGestureRecognizer<double> {
+  @override
   double get _initialPendingDragDelta => 0.0;
+
+  @override
   double _getDragDelta(PointerEvent event) => event.delta.dx;
+
+  @override
   bool get _hasSufficientPendingDragDeltaToAccept => _pendingDragDelta.abs() > kTouchSlop;
 
+  @override
   String toStringShort() => 'horizontal drag';
 }
 
 class PanGestureRecognizer extends _DragGestureRecognizer<Offset> {
+  @override
   Offset get _initialPendingDragDelta => Offset.zero;
+
+  @override
   Offset _getDragDelta(PointerEvent event) => event.delta;
+
+  @override
   bool get _hasSufficientPendingDragDeltaToAccept {
     return _pendingDragDelta.distance > kPanSlop;
   }
 
+  @override
   String toStringShort() => 'pan';
 }

packages/flutter/lib/src/gestures/events.dart

@@ -171,6 +171,7 @@ abstract class PointerEvent {
   /// the stylus is flat on that surface).
   final double tilt;
 
+  @override
   String toString() => '$runtimeType($position)';
 
   String toStringFull() {

packages/flutter/lib/src/gestures/hit_test.dart

@@ -25,6 +25,7 @@ class HitTestEntry {
   /// The [HitTestTarget] encountered during the hit test.
   final HitTestTarget target;
 
+  @override
   String toString() => '$target';
 }
 
@@ -49,5 +50,6 @@ class HitTestResult {
     path.add(entry);
   }
 
+  @override
   String toString() => 'HitTestResult(${path.isEmpty ? "<empty path>" : path.join(", ")})';
 }

packages/flutter/lib/src/gestures/long_press.dart

@@ -15,16 +15,19 @@ class LongPressGestureRecognizer extends PrimaryPointerGestureRecognizer {
 
   GestureLongPressCallback onLongPress;
 
+  @override
   void didExceedDeadline() {
     resolve(GestureDisposition.accepted);
     if (onLongPress != null)
       onLongPress();
   }
 
+  @override
   void handlePrimaryPointer(PointerEvent event) {
     if (event is PointerUpEvent)
       resolve(GestureDisposition.rejected);
   }
 
+  @override
   String toStringShort() => 'long press';
 }

packages/flutter/lib/src/gestures/lsq_solver.dart

@@ -36,6 +36,7 @@ class _Vector {
 
   double norm() => math.sqrt(this * this);
 
+  @override
   String toString() {
     String result = "";
     for (int i = 0; i < _length; i++) {
@@ -68,6 +69,7 @@ class _Matrix {
     _columns
   );
 
+  @override
   String toString() {
     String result = "";
     for (int i = 0; i < _rows; i++) {

packages/flutter/lib/src/gestures/multidrag.dart

@@ -125,6 +125,7 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
 
   Map<int, T> _pointers = <int, T>{};
 
+  @override
   void addPointer(PointerDownEvent event) {
     assert(_pointers != null);
     assert(event.pointer != null);
@@ -163,6 +164,7 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
     }
   }
 
+  @override
   void acceptGesture(int pointer) {
     assert(_pointers != null);
     T state = _pointers[pointer];
@@ -186,6 +188,7 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
     return drag;
   }
 
+  @override
   void rejectGesture(int pointer) {
     assert(_pointers != null);
     if (_pointers.containsKey(pointer)) {
@@ -204,6 +207,7 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
     _pointers.remove(pointer);
   }
 
+  @override
   void dispose() {
     for (int pointer in _pointers.keys)
       _removeState(pointer);
@@ -217,22 +221,26 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
 class _ImmediatePointerState extends MultiDragPointerState {
   _ImmediatePointerState(Point initialPosition) : super(initialPosition);
 
+  @override
   void checkForResolutionAfterMove() {
     assert(pendingDelta != null);
     if (pendingDelta.distance > kTouchSlop)
       resolve(GestureDisposition.accepted);
   }
 
+  @override
   void accepted(GestureMultiDragStartCallback starter) {
     starter(initialPosition);
   }
 }
 
 class ImmediateMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_ImmediatePointerState> {
+  @override
   _ImmediatePointerState createNewPointerState(PointerDownEvent event) {
     return new _ImmediatePointerState(event.position);
   }
 
+  @override
   String toStringShort() => 'multidrag';
 }
 
@@ -240,22 +248,26 @@ class ImmediateMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_Im
 class _HorizontalPointerState extends MultiDragPointerState {
   _HorizontalPointerState(Point initialPosition) : super(initialPosition);
 
+  @override
   void checkForResolutionAfterMove() {
     assert(pendingDelta != null);
     if (pendingDelta.dx.abs() > kTouchSlop)
       resolve(GestureDisposition.accepted);
   }
 
+  @override
   void accepted(GestureMultiDragStartCallback starter) {
     starter(initialPosition);
   }
 }
 
 class HorizontalMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_HorizontalPointerState> {
+  @override
   _HorizontalPointerState createNewPointerState(PointerDownEvent event) {
     return new _HorizontalPointerState(event.position);
   }
 
+  @override
   String toStringShort() => 'horizontal multidrag';
 }
 
@@ -263,22 +275,26 @@ class HorizontalMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_H
 class _VerticalPointerState extends MultiDragPointerState {
   _VerticalPointerState(Point initialPosition) : super(initialPosition);
 
+  @override
   void checkForResolutionAfterMove() {
     assert(pendingDelta != null);
     if (pendingDelta.dy.abs() > kTouchSlop)
       resolve(GestureDisposition.accepted);
   }
 
+  @override
   void accepted(GestureMultiDragStartCallback starter) {
     starter(initialPosition);
   }
 }
 
 class VerticalMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_VerticalPointerState> {
+  @override
   _VerticalPointerState createNewPointerState(PointerDownEvent event) {
     return new _VerticalPointerState(event.position);
   }
 
+  @override
   String toStringShort() => 'vertical multidrag';
 }
 
@@ -306,6 +322,7 @@ class _DelayedPointerState extends MultiDragPointerState {
     assert(_starter == null);
   }
 
+  @override
   void accepted(GestureMultiDragStartCallback starter) {
     assert(_starter == null);
     if (_timer == null)
@@ -314,6 +331,7 @@ class _DelayedPointerState extends MultiDragPointerState {
       _starter = starter;
   }
 
+  @override
   void checkForResolutionAfterMove() {
     assert(_timer != null);
     assert(pendingDelta != null);
@@ -321,6 +339,7 @@ class _DelayedPointerState extends MultiDragPointerState {
       resolve(GestureDisposition.rejected);
   }
 
+  @override
   void dispose() {
     _timer?.cancel();
     _timer = null;
@@ -342,9 +361,11 @@ class DelayedMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_Dela
     _delay = value;
   }
 
+  @override
   _DelayedPointerState createNewPointerState(PointerDownEvent event) {
     return new _DelayedPointerState(event.position, _delay);
   }
 
+  @override
   String toStringShort() => 'long multidrag';
 }

packages/flutter/lib/src/gestures/multitap.dart

@@ -82,6 +82,7 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
   _TapTracker _firstTap;
   final Map<int, _TapTracker> _trackers = new Map<int, _TapTracker>();
 
+  @override
   void addPointer(PointerEvent event) {
     // Ignore out-of-bounds second taps.
     if (_firstTap != null &&
@@ -112,8 +113,10 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
     }
   }
 
+  @override
   void acceptGesture(int pointer) { }
 
+  @override
   void rejectGesture(int pointer) {
     _TapTracker tracker = _trackers[pointer];
     // If tracker isn't in the list, check if this is the first tap tracker
@@ -138,6 +141,7 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
       _reset();
   }
 
+  @override
   void dispose() {
     _reset();
   }
@@ -198,6 +202,7 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
     }
   }
 
+  @override
   String toStringShort() => 'double tap';
 }
 
@@ -255,6 +260,7 @@ class _TapGesture extends _TapTracker {
     }
   }
 
+  @override
   void stopTrackingPointer(PointerRoute route) {
     _timer?.cancel();
     _timer = null;
@@ -305,6 +311,7 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
 
   final Map<int, _TapGesture> _gestureMap = new Map<int, _TapGesture>();
 
+  @override
   void addPointer(PointerEvent event) {
     assert(!_gestureMap.containsKey(event.pointer));
     _gestureMap[event.pointer] = new _TapGesture(
@@ -316,12 +323,14 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
       onTapDown(event.position, event.pointer);
   }
 
+  @override
   void acceptGesture(int pointer) {
     assert(_gestureMap.containsKey(pointer));
     _gestureMap[pointer]?.accept();
     assert(!_gestureMap.containsKey(pointer));
   }
 
+  @override
   void rejectGesture(int pointer) {
     assert(_gestureMap.containsKey(pointer));
     _gestureMap[pointer]?.reject();
@@ -347,6 +356,7 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
       onLongTapDown(lastPosition, pointer);
   }
 
+  @override
   void dispose() {
     List<_TapGesture> localGestures = new List<_TapGesture>.from(_gestureMap.values);
     for (_TapGesture gesture in localGestures)
@@ -355,5 +365,6 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
     assert(_gestureMap.isEmpty);
   }
 
+  @override
   String toStringShort() => 'multitap';
 }

packages/flutter/lib/src/gestures/recognizer.dart

@@ -61,8 +61,13 @@ abstract class OneSequenceGestureRecognizer extends GestureRecognizer {
   final Set<int> _trackedPointers = new HashSet<int>();
 
   void handleEvent(PointerEvent event);
+
+  @override
   void acceptGesture(int pointer) { }
+
+  @override
   void rejectGesture(int pointer) { }
+
   void didStopTrackingLastPointer(int pointer);
 
   void resolve(GestureDisposition disposition) {
@@ -72,6 +77,7 @@ abstract class OneSequenceGestureRecognizer extends GestureRecognizer {
       entry.resolve(disposition);
   }
 
+  @override
   void dispose() {
     resolve(GestureDisposition.rejected);
     for (int pointer in _trackedPointers)
@@ -116,6 +122,7 @@ abstract class PrimaryPointerGestureRecognizer extends OneSequenceGestureRecogni
   Point initialPosition;
   Timer _timer;
 
+  @override
   void addPointer(PointerDownEvent event) {
     startTrackingPointer(event.pointer);
     if (state == GestureRecognizerState.ready) {
@@ -127,6 +134,7 @@ abstract class PrimaryPointerGestureRecognizer extends OneSequenceGestureRecogni
     }
   }
 
+  @override
   void handleEvent(PointerEvent event) {
     assert(state != GestureRecognizerState.ready);
     if (state == GestureRecognizerState.possible && event.pointer == primaryPointer) {
@@ -151,6 +159,7 @@ abstract class PrimaryPointerGestureRecognizer extends OneSequenceGestureRecogni
     assert(deadline == null);
   }
 
+  @override
   void rejectGesture(int pointer) {
     if (pointer == primaryPointer) {
       _stopTimer();
@@ -158,11 +167,13 @@ abstract class PrimaryPointerGestureRecognizer extends OneSequenceGestureRecogni
     }
   }
 
+  @override
   void didStopTrackingLastPointer(int pointer) {
     _stopTimer();
     state = GestureRecognizerState.ready;
   }
 
+  @override
   void dispose() {
     _stopTimer();
     super.dispose();

packages/flutter/lib/src/gestures/scale.dart

@@ -31,6 +31,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
 
   double get _scaleFactor => _initialSpan > 0.0 ? _currentSpan / _initialSpan : 1.0;
 
+  @override
   void addPointer(PointerEvent event) {
     startTrackingPointer(event.pointer);
     if (_state == ScaleState.ready) {
@@ -41,6 +42,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
     }
   }
 
+  @override
   void handleEvent(PointerEvent event) {
     assert(_state != ScaleState.ready);
     bool configChanged = false;
@@ -101,6 +103,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
       onUpdate(_scaleFactor, focalPoint);
   }
 
+  @override
   void acceptGesture(int pointer) {
     if (_state != ScaleState.accepted) {
       _state = ScaleState.accepted;
@@ -108,6 +111,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
     }
   }
 
+  @override
   void didStopTrackingLastPointer(int pointer) {
     switch(_state) {
       case ScaleState.possible:
@@ -125,5 +129,6 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
     _state = ScaleState.ready;
   }
 
+  @override
   String toStringShort() => 'scale';
 }

packages/flutter/lib/src/gestures/tap.dart

@@ -27,6 +27,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   bool _wonArena = false;
   Point _finalPosition;
 
+  @override
   void handlePrimaryPointer(PointerEvent event) {
     if (event is PointerUpEvent) {
       _finalPosition = event.position;
@@ -34,6 +35,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     }
   }
 
+  @override
   void resolve(GestureDisposition disposition) {
     if (_wonArena && disposition == GestureDisposition.rejected) {
       if (onTapCancel != null)
@@ -43,10 +45,12 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     super.resolve(disposition);
   }
 
+  @override
   void didExceedDeadline() {
     _checkDown();
   }
 
+  @override
   void acceptGesture(int pointer) {
     super.acceptGesture(pointer);
     if (pointer == primaryPointer) {
@@ -56,6 +60,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     }
   }
 
+  @override
   void rejectGesture(int pointer) {
     super.rejectGesture(pointer);
     if (pointer == primaryPointer) {
@@ -91,5 +96,6 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     _finalPosition = null;
   }
 
+  @override
   String toStringShort() => 'tap';
 }

packages/flutter/lib/src/gestures/velocity_tracker.dart

@@ -17,6 +17,7 @@ class _Estimate {
   final int degree;
   final double confidence;
 
+  @override
   String toString() {
     return 'Estimate(xCoefficients: $xCoefficients, '
                     'yCoefficients: $yCoefficients, '
@@ -73,6 +74,7 @@ class _LeastSquaresVelocityTrackerStrategy extends _VelocityTrackerStrategy {
   _WeightChooser _chooseWeight;
   int _index;
 
+  @override
   void addMovement(Duration timeStamp, Point position) {
     _index += 1;
     if (_index == kHistorySize)
@@ -82,6 +84,7 @@ class _LeastSquaresVelocityTrackerStrategy extends _VelocityTrackerStrategy {
     movement.position = position;
   }
 
+  @override
   _Estimate getEstimate() {
     // Iterate over movement samples in reverse time order and collect samples.
     List<double> x = new List<double>();
@@ -145,6 +148,7 @@ class _LeastSquaresVelocityTrackerStrategy extends _VelocityTrackerStrategy {
     );
   }
 
+  @override
   void clear() {
     _index = -1;
   }
@@ -228,6 +232,7 @@ class Velocity {
         pixelsPerSecond: pixelsPerSecond + other.pixelsPerSecond);
   }
 
+  @override
   bool operator ==(dynamic other) {
     if (other is! Velocity)
       return false;
@@ -235,8 +240,10 @@ class Velocity {
     return pixelsPerSecond == typedOther.pixelsPerSecond;
   }
 
+  @override
   int get hashCode => pixelsPerSecond.hashCode;
 
+  @override
   String toString() => 'Velocity(${pixelsPerSecond.dx.toStringAsFixed(1)}, ${pixelsPerSecond.dy.toStringAsFixed(1)})';
 }
 

packages/flutter/lib/src/material/app.dart

@@ -71,14 +71,17 @@ class MaterialApp extends WidgetsApp {
   /// Only available in checked mode.
   final bool debugShowMaterialGrid;
 
+  @override
   _MaterialAppState createState() => new _MaterialAppState();
 }
 
 class _MaterialAppState extends WidgetsAppState<MaterialApp> {
-
   final HeroController _heroController = new HeroController();
+
+  @override
   NavigatorObserver get navigatorObserver => _heroController;
 
+  @override
   Widget build(BuildContext context) {
     ThemeData theme = config.theme ?? new ThemeData.fallback();
     Widget result = new AnimatedTheme(

packages/flutter/lib/src/material/app_bar.dart

@@ -67,6 +67,7 @@ class AppBar extends StatelessWidget {
     );
   }
 
+  @override
   Widget build(BuildContext context) {
     Color color = backgroundColor;
     IconThemeData iconThemeData;

packages/flutter/lib/src/material/bottom_sheet.dart

@@ -32,6 +32,7 @@ class BottomSheet extends StatefulWidget {
   final VoidCallback onClosing;
   final WidgetBuilder builder;
 
+  @override
   _BottomSheetState createState() => new _BottomSheetState();
 
   static AnimationController createAnimationController() {
@@ -75,6 +76,7 @@ class _BottomSheetState extends State<BottomSheet> {
     }
   }
 
+  @override
   Widget build(BuildContext context) {
     return new GestureDetector(
       onVerticalDragUpdate: _handleDragUpdate,
@@ -99,6 +101,7 @@ class _ModalBottomSheetLayout extends SingleChildLayoutDelegate {
 
   final double progress;
 
+  @override
   BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
     return new BoxConstraints(
       minWidth: constraints.maxWidth,
@@ -108,10 +111,12 @@ class _ModalBottomSheetLayout extends SingleChildLayoutDelegate {
     );
   }
 
+  @override
   Offset getPositionForChild(Size size, Size childSize) {
     return new Offset(0.0, size.height - childSize.height * progress);
   }
 
+  @override
   bool shouldRelayout(_ModalBottomSheetLayout oldDelegate) {
     return progress != oldDelegate.progress;
   }
@@ -122,10 +127,12 @@ class _ModalBottomSheet<T> extends StatefulWidget {
 
   final _ModalBottomSheetRoute<T> route;
 
+  @override
   _ModalBottomSheetState<T> createState() => new _ModalBottomSheetState<T>();
 }
 
 class _ModalBottomSheetState<T> extends State<_ModalBottomSheet<T>> {
+  @override
   Widget build(BuildContext context) {
     return new GestureDetector(
       onTap: () => Navigator.pop(context),
@@ -156,14 +163,21 @@ class _ModalBottomSheetRoute<T> extends PopupRoute<T> {
 
   final WidgetBuilder builder;
 
+  @override
   Duration get transitionDuration => _kBottomSheetDuration;
+
+  @override
   bool get barrierDismissable => true;
+
+  @override
   Color get barrierColor => Colors.black54;
 
+  @override
   AnimationController createAnimationController() {
     return BottomSheet.createAnimationController();
   }
 
+  @override
   Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> forwardAnimation) {
     return new _ModalBottomSheet<T>(route: this);
   }

packages/flutter/lib/src/material/button.dart

@@ -31,6 +31,7 @@ class ButtonTheme extends InheritedWidget {
     return result?.color ?? ButtonColor.normal;
   }
 
+  @override
   bool updateShouldNotify(ButtonTheme old) => color != old.color;
 }
 
@@ -63,6 +64,7 @@ abstract class MaterialButton extends StatefulWidget {
   /// enable a button, set its [onPressed] property to a non-null value.
   bool get enabled => onPressed != null;
 
+  @override
   void debugFillDescription(List<String> description) {
     super.debugFillDescription(description);
     if (!enabled)
@@ -110,6 +112,7 @@ abstract class MaterialButtonState<T extends MaterialButton> extends State<T> {
     });
   }
 
+  @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     Widget contents = new InkWell(

packages/flutter/lib/src/material/card.dart

@@ -17,6 +17,7 @@ class Card extends StatelessWidget {
   final Widget child;
   final Color color;
 
+  @override
   Widget build(BuildContext context) {
     return new Container(
       margin: _kCardMargins,

packages/flutter/lib/src/material/checkbox.dart

@@ -37,6 +37,7 @@ class Checkbox extends StatelessWidget {
   final Color activeColor;
   final ValueChanged<bool> onChanged;
 
+  @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     ThemeData themeData = Theme.of(context);
@@ -67,6 +68,7 @@ class _CheckboxRenderObjectWidget extends LeafRenderObjectWidget {
   final Color inactiveColor;
   final ValueChanged<bool> onChanged;
 
+  @override
   _RenderCheckbox createRenderObject(BuildContext context) => new _RenderCheckbox(
     value: value,
     activeColor: activeColor,
@@ -74,6 +76,7 @@ class _CheckboxRenderObjectWidget extends LeafRenderObjectWidget {
     onChanged: onChanged
   );
 
+  @override
   void updateRenderObject(BuildContext context, _RenderCheckbox renderObject) {
     renderObject
       ..value = value
@@ -103,6 +106,7 @@ class _RenderCheckbox extends RenderToggleable {
     size: const Size(2 * kRadialReactionRadius, 2 * kRadialReactionRadius)
   );
 
+  @override
   void paint(PaintingContext context, Offset offset) {
     final Canvas canvas = context.canvas;
     final double offsetX = _kOffset + offset.dx;

packages/flutter/lib/src/material/chip.dart

@@ -33,6 +33,7 @@ class Chip extends StatelessWidget {
   final Widget label;
   final VoidCallback onDeleted;
 
+  @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     final bool deletable = onDeleted != null;

packages/flutter/lib/src/material/circle_avatar.dart

@@ -19,6 +19,7 @@ class CircleAvatar extends StatelessWidget {
   final Color backgroundColor;
   final double radius;
 
+  @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final Color color = backgroundColor ?? theme.primaryColor;

packages/flutter/lib/src/material/date_picker.dart

@@ -34,6 +34,7 @@ class DatePicker extends StatefulWidget {
   final DateTime firstDate;
   final DateTime lastDate;
 
+  @override
   _DatePickerState createState() => new _DatePickerState();
 }
 
@@ -64,6 +65,7 @@ class _DatePickerState extends State<DatePicker> {
 
   static const double _calendarHeight = 210.0;
 
+  @override
   Widget build(BuildContext context) {
     Widget header = new _DatePickerHeader(
       selectedDate: config.selectedDate,
@@ -120,6 +122,7 @@ class _DatePickerHeader extends StatelessWidget {
       onModeChanged(value);
   }
 
+  @override
   Widget build(BuildContext context) {
     ThemeData theme = Theme.of(context);
     TextTheme headerTheme = theme.primaryTextTheme;
@@ -181,6 +184,7 @@ class DayPicker extends StatelessWidget {
   final ValueChanged<DateTime> onChanged;
   final DateTime displayedMonth;
 
+  @override
   Widget build(BuildContext context) {
     ThemeData themeData = Theme.of(context);
     TextStyle headerStyle = themeData.textTheme.caption.copyWith(fontWeight: FontWeight.w700);
@@ -289,10 +293,12 @@ class MonthPicker extends StatefulWidget {
   final DateTime lastDate;
   final double itemExtent;
 
+  @override
   _MonthPickerState createState() => new _MonthPickerState();
 }
 
 class _MonthPickerState extends State<MonthPicker> {
+  @override
   void initState() {
     super.initState();
     _updateCurrentDate();
@@ -335,6 +341,7 @@ class _MonthPickerState extends State<MonthPicker> {
     return result;
   }
 
+  @override
   Widget build(BuildContext context) {
     return new ScrollableLazyList(
       itemExtent: config.itemExtent,
@@ -343,6 +350,7 @@ class _MonthPickerState extends State<MonthPicker> {
     );
   }
 
+  @override
   void dispose() {
     if (_timer != null)
       _timer.cancel();
@@ -369,6 +377,7 @@ class YearPicker extends StatefulWidget {
   final DateTime firstDate;
   final DateTime lastDate;
 
+  @override
   _YearPickerState createState() => new _YearPickerState();
 }
 
@@ -403,6 +412,7 @@ class _YearPickerState extends State<YearPicker> {
     return items;
   }
 
+  @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     return new ScrollableLazyList(

packages/flutter/lib/src/material/date_picker_dialog.dart

@@ -22,10 +22,12 @@ class _DatePickerDialog extends StatefulWidget {
   final DateTime firstDate;
   final DateTime lastDate;
 
+  @override
   _DatePickerDialogState createState() => new _DatePickerDialogState();
 }
 
 class _DatePickerDialogState extends State<_DatePickerDialog> {
+  @override
   void initState() {
     super.initState();
     _selectedDate = config.initialDate;
@@ -47,6 +49,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
     Navigator.pop(context, _selectedDate);
   }
 
+  @override
   Widget build(BuildContext context) {
     return new Dialog(
       content: new DatePicker(

packages/flutter/lib/src/material/dialog.dart

@@ -54,6 +54,7 @@ class Dialog extends StatelessWidget {
     }
   }
 
+  @override
   Widget build(BuildContext context) {
 
     List<Widget> dialogBody = new List<Widget>();
@@ -123,14 +124,21 @@ class _DialogRoute<T> extends PopupRoute<T> {
 
   final Widget child;
 
+  @override
   Duration get transitionDuration => const Duration(milliseconds: 150);
+
+  @override
   bool get barrierDismissable => true;
+
+  @override
   Color get barrierColor => Colors.black54;
 
+  @override
   Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> forwardAnimation) {
     return child;
   }
 
+  @override
   Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> forwardAnimation, Widget child) {
     return new FadeTransition(
       opacity: new CurvedAnimation(

packages/flutter/lib/src/material/divider.dart

@@ -15,6 +15,7 @@ class Divider extends StatelessWidget {
   final double indent;
   final Color color;
 
+  @override
   Widget build(BuildContext context) {
     final double bottom = (height ~/ 2.0).toDouble();
     return new Container(

packages/flutter/lib/src/material/drawer.dart

@@ -36,6 +36,7 @@ class Drawer extends StatelessWidget {
   final int elevation;
   final Widget child;
 
+  @override
   Widget build(BuildContext context) {
     return new ConstrainedBox(
       constraints: const BoxConstraints.expand(width: _kWidth),
@@ -55,10 +56,12 @@ class DrawerController extends StatefulWidget {
 
   final Widget child;
 
+  @override
   DrawerControllerState createState() => new DrawerControllerState();
 }
 
 class DrawerControllerState extends State<DrawerController> {
+  @override
   void initState() {
     super.initState();
     _controller = new AnimationController(duration: _kBaseSettleDuration)
@@ -66,6 +69,7 @@ class DrawerControllerState extends State<DrawerController> {
       ..addStatusListener(_animationStatusChanged);
   }
 
+  @override
   void dispose() {
     _controller
       ..removeListener(_animationChanged)
@@ -158,6 +162,7 @@ class DrawerControllerState extends State<DrawerController> {
   final ColorTween _color = new ColorTween(begin: Colors.transparent, end: Colors.black54);
   final GlobalKey _gestureDetectorKey = new GlobalKey();
 
+  @override
   Widget build(BuildContext context) {
     if (_controller.status == AnimationStatus.dismissed) {
       return new Align(