cc: Add support for partial swaps when using impl-side painting.

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index 64be55ceae4fa38ee853913895e39122acb7bd9f..d87b881a6c0eb2b210ae26ddbe69a78d4061bb13 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -453,6 +453,12 @@ class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
 
   const gfx::RectF& update_rect() const { return update_rect_; }
 
+  void UnionDamageRect(gfx::Rect damage_rect);

[enne (OOO), 2014/04/14 17:08:29]

Can you name this function to be in the right space, e.g. UnionDamageLayerRect
or UnionDamageContentRect?

You are incorrectly unioning content space rects with layer rects.

[reveman, 2014/04/14 20:03:07]

Also, maybe more consistent to have this be SetDamageContentRect and leave it up
to the caller to do a union with damage_content_rect() if necessary?

[sohanjg, 2014/04/15 10:03:48]

Done.

[sohanjg, 2014/04/15 10:03:48]

In that case, the caller(LTHI) needs to maintain the unified damage rect for
each layer id, again involving a map.

+
+  void ResetDamageRect() { damage_rect_ = gfx::Rect(); }
+
+  const gfx::Rect& damage_rect() const { return damage_rect_; }
+
   virtual base::DictionaryValue* LayerTreeAsJson() const;
 
   void SetStackingOrderChanged(bool stacking_order_changed);
@@ -651,6 +657,8 @@ class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
   // Uses layer (not content) space.
   gfx::RectF update_rect_;
 
+  gfx::Rect damage_rect_;
+
   // Manages animations for this layer.
   scoped_refptr<LayerAnimationController> layer_animation_controller_;