cc: Invalidate the full tiled layer when contents scale changes.

cc/contents_scaling_layer.h

Index: cc/contents_scaling_layer.h
diff --git a/cc/contents_scaling_layer.h b/cc/contents_scaling_layer.h
index 81b51ff836748d32b4f38a1870454d9c24e38d03..c535d049dac1269d261c468ee15c585eee7a7e90 100644
--- a/cc/contents_scaling_layer.h
+++ b/cc/contents_scaling_layer.h
@@ -21,11 +21,20 @@ class CC_EXPORT ContentsScalingLayer : public Layer {
       gfx::Size* content_bounds) OVERRIDE;
   virtual void didUpdateBounds() OVERRIDE;
 
+  virtual void update(
+    ResourceUpdateQueue& queue,
+    const OcclusionTracker* occlusion,
+    RenderingStats& stats) OVERRIDE;
+
  protected:
   ContentsScalingLayer();
   virtual ~ContentsScalingLayer();
 
   gfx::Size computeContentBoundsForScale(float scaleX, float scaleY) const;
+
+ private:
+  float last_update_contents_scale_x_;
+  float last_update_contents_scale_y_;
 };
 
 }  // namespace cc