Fix ProgressIndicators and add a regression test

Added some unit test infrasture for checking layers.

packages/flutter/lib/widgets/progress_indicator.dart

@@ -31,6 +31,7 @@ abstract class ProgressIndicator extends StatefulComponent {
   double get _animationValue => (_animation.variable as AnimatedValue<double>).value;
   Color get _backgroundColor => Theme.of(this).primarySwatch[200];
   Color get _valueColor => Theme.of(this).primaryColor;
+  Object get _customPaintToken => value != null ? value : _animationValue;
 
   void initState() {
     _animation = new AnimationPerformance()
@@ -92,7 +93,7 @@ class LinearProgressIndicator extends ProgressIndicator {
 
   Widget _buildIndicator() {
     return new Container(
-      child: new CustomPaint(callback: _paint),
+      child: new CustomPaint(callback: _paint, token: _customPaintToken),
       constraints: new BoxConstraints.tightFor(
         width: double.INFINITY,
         height: _kLinearProgressIndicatorHeight
@@ -138,7 +139,7 @@ class CircularProgressIndicator extends ProgressIndicator {
 
   Widget _buildIndicator() {
     return new Container(
-      child: new CustomPaint(callback: _paint),
+      child: new CustomPaint(callback: _paint, token: _customPaintToken),
       constraints: new BoxConstraints(
         minWidth: _kMinCircularProgressIndicatorSize,
         minHeight: _kMinCircularProgressIndicatorSize

packages/unit/test/widget/build_utils.dart

@@ -9,6 +9,7 @@ class TestRenderView extends RenderView {
     attach();
     rootConstraints = new ViewConstraints(size: _kTestViewSize);
     scheduleInitialLayout();
+    scheduleInitialPaint(new TransformLayer(transform: new Matrix4.identity()));
   }
 }
 
@@ -63,6 +64,20 @@ class WidgetTester {
   TestApp _app;
   RenderView _renderView;
 
+  List<Layer> _layers(Layer layer) {
+    List<Layer> result = [layer];
+    if (layer is ContainerLayer) {
+      ContainerLayer root = layer;
+      Layer child = root.firstChild;
+      while(child != null) {
+        result.addAll(_layers(child));
+        child = child.nextSibling;
+      }
+    }
+    return result;
+  }
+  List<Layer> get layers => _layers(_renderView.layer);
+
   void walkWidgets(WidgetTreeWalker walker) {
     void walk(Widget widget) {
       walker(widget);
@@ -113,4 +128,14 @@ class WidgetTester {
     Component.flushBuild();
     RenderObject.flushLayout();
   }
+
+  // TODO(hansmuller): just having one pumpFrame() fn would be preferable.
+  void pumpPaintFrame(WidgetBuilder builder) {
+    _app.builder = builder;
+    Component.flushBuild();
+    RenderObject.flushLayout();
+    _renderView.updateCompositingBits();
+    RenderObject.flushPaint();
+  }
+
 }

packages/unit/test/widget/progress_indicator_test.dart

+
+import 'package:sky/rendering.dart';
+import 'package:sky/widgets.dart';
+import 'package:test/test.dart';
+
+import 'build_utils.dart';
+
+void main() {
+  test('LinearProgressIndicator changes when its value changes', () {
+    WidgetTester tester = new WidgetTester();
+
+    tester.pumpPaintFrame(() {
+      return new Block([new LinearProgressIndicator(value: 0.0)]);
+    });
+    List<Layer> layers1 = tester.layers;
+
+    tester.pumpPaintFrame(() {
+      return new Block([new LinearProgressIndicator(value: 0.5)]);
+    });
+    List<Layer> layers2 = tester.layers;
+
+    expect(layers1, isNot(equals(layers2)));
+  });
+}