Add @override annotation to known overriden methods

sky/sdk/example/game/lib/sprite.dart

Index: sky/sdk/example/game/lib/sprite.dart
diff --git a/sky/sdk/example/game/lib/sprite.dart b/sky/sdk/example/game/lib/sprite.dart
index 0eea48006110fdd99f8bb659a3adafb37442a5d8..2f5ec5e3d5338e69c0bb21d0855521013b994ac5 100644
--- a/sky/sdk/example/game/lib/sprite.dart
+++ b/sky/sdk/example/game/lib/sprite.dart
@@ -64,6 +64,7 @@ class Sprite extends NodeWithSize {
     _opacity = opacity;
   }
 
+  @override
   void paint(PaintingCanvas canvas) {
     canvas.save();
 
@@ -75,10 +76,10 @@ class Sprite extends NodeWithSize {
       double h = texture.size.height;
 
       if (w <= 0 || h <= 0) return;
-      
+
       double scaleX = size.width / w;
       double scaleY = size.height / h;
-      
+
       if (constrainProportions) {
         // Constrain proportions, using the smallest scale and by centering the image
         if (scaleX < scaleY) {
@@ -89,7 +90,7 @@ class Sprite extends NodeWithSize {
           scaleX = scaleY;
         }
       }
-      
+
       canvas.scale(scaleX, scaleY);
 
       // Setup paint object for opacity and transfer mode