[NOT FOR REVIEW] ash: Add some implementation for the window management extension API.

ash/shell/shell_delegate_impl.cc

 // Copyright (c) 2012 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 "ash/shell/shell_delegate_impl.h"
 
 #include "ash/shell/example_factory.h"
 #include "ash/shell/launcher_delegate_impl.h"
 #include "ash/shell/toplevel_window.h"
 #include "ash/shell_window_ids.h"
@@ skipping 112 matching lines @@
   return NULL;
 }
 
 aura::client::UserActionClient* ShellDelegateImpl::CreateUserActionClient() {
   return NULL;
 }
 
 void ShellDelegateImpl::OpenFeedbackPage() {
 }
 
+ash::WindowManagerExtensionDelegate*
+ShellDelegateImpl::CreateWindowManagerDelegate() {
+  return NULL;
+}
+
 void ShellDelegateImpl::RecordUserMetricsAction(UserMetricsAction action) {
 }
 
 }  // namespace shell
 }  // namespace ash