Change SingletonHwnd to be based on WindowImpl.

ui/base/win/window_impl.h

 // 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.
 
 #ifndef UI_BASE_WIN_WINDOW_IMPL_H_
 #define UI_BASE_WIN_WINDOW_IMPL_H_
 #pragma once
 
 #include <atlbase.h>
 #include <atlapp.h>
@@ skipping 12 matching lines @@
 // An interface implemented by classes that use message maps.
 // ProcessWindowMessage is implemented by the BEGIN_MESSAGE_MAP_EX macro.
 class MessageMapInterface {
  public:
   // Processes one message from the window's message queue.
   virtual BOOL ProcessWindowMessage(HWND window,
                                     UINT message,
                                     WPARAM w_param,
                                     LPARAM l_param,
                                     LRESULT& result,
-                                    DWORD msg_mad_id = 0) = 0;
+                                    DWORD msg_map_id = 0) = 0;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 //
 // WindowImpl
 //  A convenience class that encapsulates the details of creating and
 //  destroying a HWND.  This class also hosts the windows procedure used by all
 //  Windows.
 //
 ///////////////////////////////////////////////////////////////////////////////
@@ skipping 59 matching lines @@
 
   // Our hwnd.
   HWND hwnd_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowImpl);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_WIN_WINDOW_IMPL_H_