Makes tests either use mock compositor or mock WebGraphicsContext3D

chrome/browser/chrome_browser_main_extra_parts_aura.cc

 // Copyright (c) 2011 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 "chrome/browser/chrome_browser_main_extra_parts_aura.h"
+
+#include "base/command_line.h"
 #include "chrome/browser/ui/views/aura/chrome_shell_delegate.h"
 #include "chrome/browser/ui/views/aura/screen_orientation_listener.h"
+#include "chrome/common/chrome_switches.h"
 #include "ui/aura/desktop.h"
 #include "ui/aura_shell/shell.h"
+#include "ui/gfx/compositor/compositor_setup.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/system/runtime_environment.h"
 #endif
 
 ChromeBrowserMainExtraPartsAura::ChromeBrowserMainExtraPartsAura()
     : ChromeBrowserMainExtraParts() {
 }
 
 void ChromeBrowserMainExtraPartsAura::PostBrowserProcessInit() {
+  if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTestCompositor))
+    ui::SetupTestCompositor();
+
 #if defined(OS_CHROMEOS)
   if (chromeos::system::runtime_environment::IsRunningOnChromeOS())
     aura::Desktop::set_use_fullscreen_host_window(true);
 #endif
 
   // Shell takes ownership of ChromeShellDelegate.
   aura_shell::Shell::CreateInstance(new ChromeShellDelegate);
 
   // Make sure the singleton ScreenOrientationListener object is created.
   ScreenOrientationListener::GetInstance();
 }
 
 void ChromeBrowserMainExtraPartsAura::PostMainMessageLoopRun() {
   aura_shell::Shell::DeleteInstance();
   aura::Desktop::DeleteInstance();
 }