Implement cycle window forward/backward by keyboard shortcuts.

ui/aura_shell/test/aura_shell_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_shell/test/aura_shell_test_base.h"
 
 #include "ui/aura_shell/shell.h"
+#include "ui/aura_shell/test/test_shell_delegate.h"
 
 namespace aura_shell {
 namespace test {
 
 AuraShellTestBase::AuraShellTestBase() {
 }
 
 AuraShellTestBase::~AuraShellTestBase() {
 }
 
 void AuraShellTestBase::SetUp() {
   aura::test::AuraTestBase::SetUp();
 
   // Creates Shell and hook with Desktop.
-  aura_shell::Shell::CreateInstance(NULL);
+  aura_shell::Shell::CreateInstance(new TestShellDelegate);
 }
 
 void AuraShellTestBase::TearDown() {
   // Flush the message loop to finish pending release tasks.
   RunAllPendingInMessageLoop();
 
   // Tear down the shell.
   aura_shell::Shell::DeleteInstance();
 
   aura::test::AuraTestBase::TearDown();
 }
 
 }  // namespace test
 }  // namespace aura_shell