ui: Clean up damaged rects and clear them after painting.

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 3e61d40b95a2c02151bf44dd5418c2d74cc655c8..914e000feedff6be8b423b1b2aa44a573e3a6bc2 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -657,11 +657,7 @@ bool Layer::SchedulePaint(const gfx::Rect& invalid_rect) {
       type_ == LAYER_NINE_PATCH || (!delegate_ && !mailbox_.IsValid()))
     return false;
 
-  damaged_region_.op(invalid_rect.x(),
-                     invalid_rect.y(),
-                     invalid_rect.right(),
-                     invalid_rect.bottom(),
-                     SkRegion::kUnion_Op);
+  damaged_region_.Union(invalid_rect);
   ScheduleDraw();
   return true;
 }
@@ -673,20 +669,17 @@ void Layer::ScheduleDraw() {
 }
 
 void Layer::SendDamagedRects() {
-  if ((delegate_ || mailbox_.IsValid()) && !damaged_region_.isEmpty()) {
-    for (SkRegion::Iterator iter(damaged_region_); !iter.done(); iter.next()) {
-      const SkIRect& sk_damaged = iter.rect();
-      gfx::Rect damaged(
-          sk_damaged.x(),
-          sk_damaged.y(),
-          sk_damaged.width(),
-          sk_damaged.height());
-      cc_layer_->SetNeedsDisplayRect(damaged);
-    }
-    damaged_region_.setEmpty();
-  }
-  for (size_t i = 0; i < children_.size(); ++i)
-    children_[i]->SendDamagedRects();
+  if (damaged_region_.IsEmpty())
+    return;
+  if (!delegate_ && !mailbox_.IsValid())
+    return;
+
+  for (cc::Region::Iterator iter(damaged_region_); iter.has_rect(); iter.next())
+    cc_layer_->SetNeedsDisplayRect(iter.rect());
+}
+
+void Layer::ClearDamagedRects() {
+  damaged_region_.Clear();
 }
 
 void Layer::CompleteAllAnimations() {
@@ -745,6 +738,7 @@ void Layer::PaintContents(
     const gfx::Rect& clip,
     ContentLayerClient::PaintingControlSetting painting_control) {
   TRACE_EVENT1("ui", "Layer::PaintContents", "name", name_);
+  ClearDamagedRects();
   scoped_ptr<gfx::Canvas> canvas(gfx::Canvas::CreateCanvasWithoutScaling(
       sk_canvas, device_scale_factor_));
   if (delegate_)
@@ -756,15 +750,16 @@ void Layer::PaintContentsToDisplayList(
     const gfx::Rect& clip,
     ContentLayerClient::PaintingControlSetting painting_control) {
   TRACE_EVENT1("ui", "Layer::PaintContentsToDisplayList", "name", name_);
-  if (delegate_) {
-    // TODO(danakj): Save the invalidation on the layer and pass that down
-    // instead of the |clip| here. That will break everything until View
-    // early-outs emit cached display items instead of nothing.
-    gfx::Rect invalidation = clip;
-    DCHECK(clip.Contains(invalidation));
-    delegate_->OnPaintLayer(
-        PaintContext(display_list, device_scale_factor_, clip, invalidation));
-  }
+  ClearDamagedRects();
+  if (!delegate_)
+    return;
+  // TODO(danakj): Save the invalidation on the layer and pass that down
+  // instead of the |clip| here. That will break everything until View
+  // early-outs emit cached display items instead of nothing.
+  gfx::Rect invalidation = clip;
+  DCHECK(clip.Contains(invalidation));
+  delegate_->OnPaintLayer(
+      PaintContext(display_list, device_scale_factor_, clip, invalidation));
 }
 
 bool Layer::FillsBoundsCompletely() const { return fills_bounds_completely_; }