Fix white flash on certain Chromecast screen transitions.

chromecast/browser/cast_content_window.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 "chromecast/browser/cast_content_window.h"
 
 #include "base/threading/thread_restrictions.h"
 #include "chromecast/base/metrics/cast_metrics_helper.h"
 #include "content/public/browser/web_contents.h"
 #include "ipc/ipc_message.h"
@@ skipping 67 matching lines @@
     if (old_screen) {
       delete old_screen;
     }
   }
   CHECK(aura::Env::GetInstance());
   window_tree_host_.reset(
       aura::WindowTreeHost::Create(gfx::Rect(initial_size)));
   window_tree_host_->InitHost();
   window_tree_host_->window()->SetLayoutManager(
       new CastFillLayout(window_tree_host_->window()));
+  window_tree_host_->compositor()->SetBackgroundColor(SK_ColorBLACK);
 
   focus_client_.reset(new aura::test::TestFocusClient());
   aura::client::SetFocusClient(
       window_tree_host_->window(), focus_client_.get());
 
   window_tree_host_->Show();
 
   // Add and show content's view/window
   aura::Window* content_window = web_contents->GetNativeView();
   aura::Window* parent = window_tree_host_->window();
@@ skipping 14 matching lines @@
       create_params);
   content::WebContentsObserver::Observe(web_contents);
   return make_scoped_ptr(web_contents);
 }
 
 void CastContentWindow::DidFirstVisuallyNonEmptyPaint() {
   metrics::CastMetricsHelper::GetInstance()->LogTimeToFirstPaint();
 }
 
 }  // namespace chromecast