Aura-Mus: Enable Surface Synchronization behind flag

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 657 matching lines @@
   surface_layer_->SetPrimarySurfaceInfo(surface_info);
 
   frame_size_in_dip_ = gfx::ConvertSizeToDIP(surface_info.device_scale_factor(),
                                              surface_info.size_in_pixels());
   RecomputeDrawsContentAndUVRect();
 
   for (const auto& mirror : mirrors_)
     mirror->dest()->SetShowPrimarySurface(surface_info, ref_factory);
 }
 
+void Layer::SetFallbackSurface(const cc::SurfaceInfo& surface_info) {
+  DCHECK(type_ == LAYER_TEXTURED || type_ == LAYER_SOLID_COLOR);
+  DCHECK(surface_layer_);
+
+  // TODO(fsamuel): We should compute the gutter in the display compositor.
+  surface_layer_->SetFallbackSurfaceInfo(surface_info);
+
+  for (const auto& mirror : mirrors_)
+    mirror->dest()->SetFallbackSurface(surface_info);
+}
+
 void Layer::SetShowSolidColorContent() {
   DCHECK_EQ(type_, LAYER_SOLID_COLOR);
 
   if (solid_color_layer_.get())
     return;
 
   scoped_refptr<cc::SolidColorLayer> new_layer = cc::SolidColorLayer::Create();
   SwitchToLayer(new_layer);
   solid_color_layer_ = new_layer;
 
@@ skipping 488 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