Use `}) : super` consistently

Fixes #1372

examples/address_book/lib/main.dart

@@ -11,7 +11,7 @@ class Field extends StatelessComponent {
     this.inputKey,
     this.icon,
     this.placeholder
-  }): super(key: key);
+  }) : super(key: key);
 
   final GlobalKey inputKey;
   final String icon;

examples/widgets/drag_and_drop.dart

@@ -50,7 +50,7 @@ class ExampleDragTargetState extends State<ExampleDragTarget> {
 }
 
 class Dot extends StatelessComponent {
-  Dot({ Key key, this.color, this.size }): super(key: key);
+  Dot({ Key key, this.color, this.size }) : super(key: key);
   final Color color;
   final double size;
   Widget build(BuildContext context) {
@@ -66,7 +66,7 @@ class Dot extends StatelessComponent {
 }
 
 class ExampleDragSource extends StatelessComponent {
-  ExampleDragSource({ Key key, this.navigator, this.name, this.color }): super(key: key);
+  ExampleDragSource({ Key key, this.navigator, this.name, this.color }) : super(key: key);
   final NavigatorState navigator;
   final String name;
   final Color color;

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

@@ -32,7 +32,7 @@ class App extends StatefulComponent {
     this.theme,
     this.routes,
     this.onGenerateRoute
-  }): super(key: key) {
+  }) : super(key: key) {
     assert(() {
       'The "routes" argument to App() is required.';
       'This might be a sign that you have not upgraded to our new Widgets framework.';

packages/flutter/lib/src/widgets/basic.dart

@@ -910,7 +910,7 @@ class Listener extends OneChildRenderObjectWidget {
     this.onPointerMove,
     this.onPointerUp,
     this.onPointerCancel
-  }): super(key: key, child: child);
+  }) : super(key: key, child: child);
 
   final PointerEventListener onPointerDown;
   final PointerEventListener onPointerMove;

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

@@ -61,7 +61,7 @@ class _CheckboxWrapper extends LeafRenderObjectWidget {
     this.onChanged,
     this.uncheckedColor,
     this.accentColor
-  }): super(key: key) {
+  }) : super(key: key) {
     assert(uncheckedColor != null);
     assert(accentColor != null);
   }

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

@@ -30,7 +30,7 @@ class Dialog extends StatelessComponent {
     this.contentPadding,
     this.actions,
     this.onDismiss
-  }): super(key: key);
+  }) : super(key: key);
 
   /// The (optional) title of the dialog is displayed in a large font at the top
   /// of the dialog.

packages/flutter/lib/src/widgets/drag_target.dart

@@ -45,7 +45,7 @@ class Draggable extends StatefulComponent {
     this.feedback,
     this.feedbackOffset: Offset.zero,
     this.dragAnchor: DragAnchor.child
-  }): super(key: key) {
+  }) : super(key: key) {
     assert(navigator != null);
     assert(child != null);
     assert(feedback != null);

packages/flutter/lib/src/widgets/input.dart

@@ -28,7 +28,7 @@ class Input extends Scrollable {
     this.placeholder,
     this.onChanged,
     this.keyboardType: KeyboardType.TEXT
-  }): super(
+  }) : super(
     key: key,
     initialScrollOffset: 0.0,
     scrollDirection: ScrollDirection.horizontal

packages/flutter/lib/src/widgets/mixed_viewport.dart

@@ -22,7 +22,7 @@ class MixedViewport extends RenderObjectWidget {
     this.token,
     this.onExtentsUpdate,
     this.onInvalidatorAvailable
-  }): super(key: key);
+  }) : super(key: key);
 
   final double startOffset;
   final ScrollDirection direction;