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

ui/compositor/layer.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 329 matching lines @@
   void OnDeviceScaleFactorChanged(float device_scale_factor);
 
   // Notifies the layer that one of its children has received a new
   // delegated frame.
   void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip);
 
   // Requets a copy of the layer's output as a texture or bitmap.
   void RequestCopyOfOutput(scoped_ptr<cc::CopyOutputRequest> request);
 
   // ContentLayerClient
+  gfx::Rect PaintableRegion() override;

[sky, 2015/11/22 15:42:09]

Just to make sure, this is the bounds of the parent and not the bounds of this,
right?

[chrishtr, 2015/11/23 16:52:02]

It's the paintable bounds of this layer, in the local space of this layer.

   scoped_refptr<cc::DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       ContentLayerClient::PaintingControlSetting painting_control) override;
   bool FillsBoundsCompletely() const override;
   size_t GetApproximateUnsharedMemoryUsage() const override;
 
   cc::Layer* cc_layer_for_testing() { return cc_layer_; }
 
   // TextureLayerClient
   bool PrepareTextureMailbox(
@@ skipping 174 matching lines @@
   // The size of the frame or texture in DIP, set when SetShowDelegatedContent
   // or SetTextureMailbox was called.
   gfx::Size frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_