Add @override annotation to known overriden methods

sky/sdk/example/rendering/sector_layout.dart

Index: sky/sdk/example/rendering/sector_layout.dart
diff --git a/sky/sdk/example/rendering/sector_layout.dart b/sky/sdk/example/rendering/sector_layout.dart
index 24f09b3b46f308ca76748beb8a50287a6dcc1fa1..002a3aa6e92b1fc70a660fcc28d8bc2f9bb5ff46 100644
--- a/sky/sdk/example/rendering/sector_layout.dart
+++ b/sky/sdk/example/rendering/sector_layout.dart
@@ -38,6 +38,7 @@ class SectorConstraints extends Constraints {
     return clamp(min: minDeltaTheta, max: maxDeltaTheta, value: deltaTheta);
   }
 
+  @override
   bool get isTight => minDeltaTheta >= maxDeltaTheta && minDeltaTheta >= maxDeltaTheta;
 }
 
@@ -65,6 +66,7 @@ class SectorParentData extends ParentData {
 
 abstract class RenderSector extends RenderObject {
 
+  @override
   void setupParentData(RenderObject child) {
     if (child.parentData is! SectorParentData)
       child.parentData = new SectorParentData();
@@ -74,7 +76,10 @@ abstract class RenderSector extends RenderObject {
     return new SectorDimensions.withConstraints(constraints);
   }
 
+  @override
   SectorConstraints get constraints => super.constraints;
+
+  @override
   bool debugDoesMeetConstraints() {
     assert(constraints != null);
     assert(deltaRadius != null);
@@ -86,11 +91,15 @@ abstract class RenderSector extends RenderObject {
            constraints.minDeltaTheta <= deltaTheta &&
            deltaTheta <= math.max(constraints.minDeltaTheta, constraints.maxDeltaTheta);
   }
+
+  @override
   void performResize() {
     // default behaviour 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
@@ -127,6 +136,7 @@ abstract class RenderDecoratedSector extends RenderSector {
   }
 
   // offset must point to the center of the circle
+  @override
   void paint(PaintingCanvas canvas, Offset offset) {
     assert(deltaRadius != null);
     assert(deltaTheta != null);
@@ -156,6 +166,7 @@ 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) {
@@ -197,12 +208,14 @@ 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;
@@ -231,6 +244,7 @@ class RenderSectorRing extends RenderSectorWithChildren {
                                                 deltaTheta: innerTheta);
   }
 
+  @override
   void performLayout() {
     assert(this.parentData is SectorParentData);
     deltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
@@ -264,6 +278,7 @@ 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(PaintingCanvas canvas, Offset offset) {
     // TODO(ianh): avoid code duplication
     super.paint(canvas, offset);
@@ -307,12 +322,14 @@ 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);
@@ -339,6 +356,7 @@ class RenderSectorSlice extends RenderSectorWithChildren {
                                                 deltaTheta: outerDeltaTheta);
   }
 
+  @override
   void performLayout() {
     assert(this.parentData is SectorParentData);
     deltaTheta = constraints.constrainDeltaTheta(desiredDeltaTheta);
@@ -369,6 +387,7 @@ 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(PaintingCanvas canvas, Offset offset) {
     // TODO(ianh): avoid code duplication
     super.paint(canvas, offset);
@@ -407,29 +426,34 @@ class RenderBoxToRenderSectorAdapter extends RenderBox {
     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);
@@ -446,6 +470,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox {
     return constraints.constrain(new Size(dimension, dimension));
   }
 
+  @override
   void performLayout() {
     if (child == null) {
       size = constraints.constrain(Size.zero);
@@ -462,6 +487,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox {
     }
   }
 
+  @override
   void paint(PaintingCanvas canvas, Offset offset) {
     super.paint(canvas, offset);
     if (child != null) {
@@ -471,6 +497,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox {
     }
   }
 
+  @override
   bool hitTest(HitTestResult result, { Point position }) {
     double x = position.x;
     double y = position.y;
@@ -492,7 +519,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox {
     result.add(new BoxHitTestEntry(this, position));
     return true;
   }
-  
+
 }
 
 class RenderSolidColor extends RenderDecoratedSector {
@@ -506,15 +533,18 @@ 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(sky.Event event, HitTestEntry entry) {
     if (event.type == 'pointerdown')
       decoration = new BoxDecoration(backgroundColor: const Color(0xFFFF0000));