Use a mocked compositor for unit tests

ui/aura/test/aura_test_base.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 "ui/aura/test/aura_test_base.h"
 
 #if defined(OS_WIN)
 #include <ole2.h>
 #endif
 
 #include "ui/aura/desktop.h"
 #include "ui/aura/test/test_desktop_delegate.h"
-#include "ui/gfx/compositor/test_compositor.h"
 
 namespace aura {
 namespace test {
 
-static ui::Compositor* TestCreateCompositor() {
-  return new ui::TestCompositor();
-}
-
 AuraTestBase::AuraTestBase()
     : setup_called_(false),
       teardown_called_(false) {
 #if defined(OS_WIN)
   OleInitialize(NULL);
 #endif
 }
 
 AuraTestBase::~AuraTestBase() {
 #if defined(OS_WIN)
   OleUninitialize();
 #endif
   CHECK(setup_called_)
       << "You have overridden SetUp but never called super class's SetUp";
   CHECK(teardown_called_)
       << "You have overridden TearDown but never called super class's TearDown";
 }
 
 void AuraTestBase::SetUp() {
   testing::Test::SetUp();
   setup_called_ = true;
-  aura::Desktop::set_compositor_factory_for_testing(&TestCreateCompositor);
   // TestDesktopDelegate is owned by the desktop.
   new TestDesktopDelegate();
   Desktop::GetInstance()->Show();
   Desktop::GetInstance()->SetSize(gfx::Size(600, 600));
 }
 
 void AuraTestBase::TearDown() {
   // Flush the message loop because we have pending release tasks
   // and these tasks if un-executed would upset Valgrind.
   RunPendingMessages();
   teardown_called_ = true;
   testing::Test::TearDown();
-  aura::Desktop::set_compositor_factory_for_testing(NULL);
 }
 
 }  // namespace test
 }  // namespace aura