Clear ui::Layer damaged_region_ after commit.

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index f8fe81005fa3e0344cf35dd17bb781272caad521..cf42867560481ca75980736bda03a7260f4757c9 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -672,9 +672,9 @@ void Layer::SendDamagedRects() {
 
   for (cc::Region::Iterator iter(damaged_region_); iter.has_rect(); iter.next())
     cc_layer_->SetNeedsDisplayRect(iter.rect());
-}
 
-void Layer::ClearDamagedRects() {
+  if (content_layer_)
+    paint_region_.Union(damaged_region_);
   damaged_region_.Clear();
 }
 
@@ -739,8 +739,8 @@ scoped_refptr<cc::DisplayItemList> Layer::PaintContentsToDisplayList(
   TRACE_EVENT1("ui", "Layer::PaintContentsToDisplayList", "name", name_);
   gfx::Rect local_bounds(bounds().size());
   gfx::Rect invalidation(
-      gfx::IntersectRects(damaged_region_.bounds(), local_bounds));
-  ClearDamagedRects();
+      gfx::IntersectRects(paint_region_.bounds(), local_bounds));
+  paint_region_.Clear();
   cc::DisplayItemListSettings settings;
   settings.use_cached_picture = false;
   scoped_refptr<cc::DisplayItemList> display_list =