Force use of and cache render surface.

ui/compositor/layer.cc

 // 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.
 
 #include "ui/compositor/layer.h"
 
 #include <algorithm>
 #include <memory>
 #include <utility>
 
@@ skipping 636 matching lines @@
   SetLayerFilters();
   SetLayerBackgroundFilters();
 }
 
 void Layer::SwitchCCLayerForTest() {
   scoped_refptr<cc::Layer> new_layer = cc::PictureLayer::Create(this);
   SwitchToLayer(new_layer);
   content_layer_ = new_layer;
 }
 
+void Layer::SetCacheRenderSurface(bool cache_render_surface) {
+  cc_layer_->SetCacheRenderSurface(cache_render_surface);

[danakj, 2017/07/28 22:22:58]

You should leave a comment explaining why Clone() and SwitchToLayer() are not
preserving this, if it is intentional.

[danakj, 2017/07/28 22:32:45]

Adding a comment to explain why not propogated to the new layer in Clone, and
making it preserve it in SwitchToLayer() would LGTM

[wutao, 2017/07/28 23:38:58]

Added a comment and two tests for cloning and switching cc_layer.

+}
+
 void Layer::SetTextureMailbox(
     const viz::TextureMailbox& mailbox,
     std::unique_ptr<viz::SingleReleaseCallback> release_callback,
     gfx::Size texture_size_in_dip) {
   DCHECK(type_ == LAYER_TEXTURED || type_ == LAYER_SOLID_COLOR);
   DCHECK(mailbox.IsValid());
   DCHECK(release_callback);
   if (!texture_layer_.get()) {
     scoped_refptr<cc::TextureLayer> new_layer =
         cc::TextureLayer::CreateForMailbox(this);
@@ skipping 587 matching lines @@
   const auto it = std::find_if(mirrors_.begin(), mirrors_.end(),
       [mirror](const std::unique_ptr<LayerMirror>& mirror_ptr) {
         return mirror_ptr.get() == mirror;
       });
 
   DCHECK(it != mirrors_.end());
   mirrors_.erase(it);
 }
 
 }  // namespace ui