Clear ui::Layer damaged_region_ after commit.

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index 57c2a5a69b9fa7a134eb46dd41227cd80ad3c1fb..f5d4526142669b2b692cce0a08eb963c72153d57 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -334,7 +334,6 @@ class COMPOSITOR_EXPORT Layer
   // Uses damaged rectangles recorded in |damaged_region_| to invalidate the
   // |cc_layer_|.
   void SendDamagedRects();
-  void ClearDamagedRects();
 
   const cc::Region& damaged_region() const { return damaged_region_; }
 
@@ -380,6 +379,10 @@ class COMPOSITOR_EXPORT Layer
   // Triggers a call to SwitchToLayer.
   void SwitchCCLayerForTest();
 
+  const cc::Region& damaged_region_for_testing() const {
+    return damaged_region_;
+  }
+
  private:
   friend class LayerOwner;
 
@@ -450,9 +453,13 @@ class COMPOSITOR_EXPORT Layer
   bool fills_bounds_opaquely_;
   bool fills_bounds_completely_;
 
+  // Union of damaged rects, in layer space, that SetNeedsDisplayRect should
+  // be called on.
+  cc::Region damaged_region_;
+
   // Union of damaged rects, in layer space, to be used when compositor is ready
   // to paint the content.
-  cc::Region damaged_region_;
+  cc::Region paint_region_;
 
   int background_blur_radius_;