Turn off computation of the interest rect in cc in synchronized paint mode.

cc/blink/web_content_layer_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/blink/web_content_layer_impl.h"
 
 #include "base/command_line.h"
 #include "cc/base/switches.h"
 #include "cc/blink/web_display_item_list_impl.h"
 #include "cc/layers/picture_layer.h"
@@ skipping 40 matching lines @@
 }
 
 WebContentLayerImpl::~WebContentLayerImpl() {
   static_cast<PictureLayer*>(layer_->layer())->ClearClient();
 }
 
 blink::WebLayer* WebContentLayerImpl::layer() {
   return layer_.get();
 }
 
+gfx::Rect WebContentLayerImpl::PaintableRegion() {
+  return client_->paintableRegion();
+}
+
 scoped_refptr<cc::DisplayItemList>
 WebContentLayerImpl::PaintContentsToDisplayList(
     const gfx::Rect& clip,
     cc::ContentLayerClient::PaintingControlSetting painting_control) {
   cc::DisplayItemListSettings settings;
   settings.use_cached_picture = UseCachedPictureRaster();
 
   scoped_refptr<cc::DisplayItemList> display_list =
       cc::DisplayItemList::Create(clip, settings);
   if (client_) {
     WebDisplayItemListImpl list(display_list.get());
     client_->paintContents(&list, clip, PaintingControlToWeb(painting_control));
   }
   display_list->Finalize();
   return display_list;
 }
 
 bool WebContentLayerImpl::FillsBoundsCompletely() const {
   return false;
 }
 
 size_t WebContentLayerImpl::GetApproximateUnsharedMemoryUsage() const {
   return client_->approximateUnsharedMemoryUsage();
 }
 
 }  // namespace cc_blink