cc: Remove the opaque rect return-parameter from ContentLayerClient.

cc/resources/layer_updater.h

Index: cc/resources/layer_updater.h
diff --git a/cc/resources/layer_updater.h b/cc/resources/layer_updater.h
index 47f44106e400e6af5f1b7d11b5c9126800d2ccb0..258d2be9a173583bcd5d734286f68d63af8bb02e 100644
--- a/cc/resources/layer_updater.h
+++ b/cc/resources/layer_updater.h
@@ -46,14 +46,10 @@ class CC_EXPORT LayerUpdater : public base::RefCounted<LayerUpdater> {
 
   virtual scoped_ptr<Resource> CreateResource(
       PrioritizedResourceManager* manager) = 0;
-  // The |resulting_opaque_rect| gives back a region of the layer that was
-  // painted opaque. If the layer is marked opaque in the updater, then this
-  // region should be ignored in preference for the entire layer's area.
   virtual void PrepareToUpdate(const gfx::Rect& content_rect,
                                const gfx::Size& tile_size,
                                float contents_width_scale,
-                               float contents_height_scale,
-                               gfx::Rect* resulting_opaque_rect) {}
+                               float contents_height_scale) {}
   virtual void ReduceMemoryUsage() {}
 
   // Set true by the layer when it is known that the entire output is going to