Surface synchronization: Don't gutter translucent windows

ui/aura/mus/client_surface_embedder.cc

 // Copyright 2017 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/aura/mus/client_surface_embedder.h"
 
 #include "cc/surfaces/surface_reference_factory.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/geometry/dip_util.h"
 
@@ skipping 58 matching lines @@
   gfx::Size fallback_surface_size_in_dip;
   const cc::SurfaceInfo* fallback_surface_info =
       surface_layer_->GetFallbackSurfaceInfo();
   if (fallback_surface_info) {
     float fallback_device_scale_factor =
         fallback_surface_info->device_scale_factor();
     fallback_surface_size_in_dip = gfx::ConvertSizeToDIP(
         fallback_device_scale_factor, fallback_surface_info->size_in_pixels());
   }
   gfx::Rect window_bounds(window_->bounds());
-  if (fallback_surface_size_in_dip.width() < window_bounds.width()) {
+  if (!window_->transparent() &&
+      fallback_surface_size_in_dip.width() < window_bounds.width()) {
     right_gutter_ = base::MakeUnique<ui::Layer>(ui::LAYER_SOLID_COLOR);
     // TODO(fsamuel): Use the embedded client's background color.
     right_gutter_->SetColor(SK_ColorWHITE);
     int width = window_bounds.width() - fallback_surface_size_in_dip.width();
     // The right gutter also includes the bottom-right corner, if necessary.
     int height = window_bounds.height() - client_area_insets_.height();
     right_gutter_->SetBounds(gfx::Rect(
         client_area_insets_.left() + fallback_surface_size_in_dip.width(),
         client_area_insets_.top(), width, height));
     window_->layer()->Add(right_gutter_.get());
   } else {
     right_gutter_.reset();
   }
 
   // Only create a bottom gutter if a fallback surface is available. Otherwise,
   // the right gutter will fill the whole window until a fallback is available.
-  if (!fallback_surface_size_in_dip.IsEmpty() &&
+  if (!window_->transparent() && !fallback_surface_size_in_dip.IsEmpty() &&
       fallback_surface_size_in_dip.height() < window_bounds.height()) {
     bottom_gutter_ = base::MakeUnique<ui::Layer>(ui::LAYER_SOLID_COLOR);
     // TODO(fsamuel): Use the embedded client's background color.
     bottom_gutter_->SetColor(SK_ColorWHITE);
     int width = fallback_surface_size_in_dip.width();
     int height = window_bounds.height() - fallback_surface_size_in_dip.height();
     bottom_gutter_->SetBounds(
         gfx::Rect(0, fallback_surface_size_in_dip.height(), width, height));
     window_->layer()->Add(bottom_gutter_.get());
   } else {
     bottom_gutter_.reset();
   }
   window_->layer()->StackAtTop(surface_layer_.get());
 }
 
 }  // namespace aura