Adds a class that makes it easy to subclass a HWND and filter messages sent to it.

ui/base/dragdrop/os_exchange_data.h

 // 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.
 
 #ifndef UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_H_
 #pragma once
 
 #include "build/build_config.h"
 
@@ skipping 32 matching lines @@
 ///////////////////////////////////////////////////////////////////////////////
 
 // NOTE: Support for html and file contents is required by TabContentViewWin.
 // TabContentsViewGtk uses a different class to handle drag support that does
 // not use OSExchangeData. As such, file contents and html support is only
 // compiled on windows.
 class UI_EXPORT OSExchangeData {
  public:
   // CustomFormats are used for non-standard data types. For example, bookmark
   // nodes are written using a CustomFormat.
-#if defined(USE_AURA)
+#if defined(USE_AURA) && !defined(OS_WIN)
   // Use the same type as the clipboard (why do we want two different
   // definitions of this on other platforms?).
   typedef Clipboard::FormatType CustomFormat;
 #elif defined(OS_WIN)
   typedef CLIPFORMAT CustomFormat;
 #elif defined(TOOLKIT_GTK)
   typedef GdkAtom CustomFormat;
 #else
   typedef void* CustomFormat;
 #endif
@@ skipping 149 matching lines @@
 
   // Provides the actual data.
   scoped_ptr<Provider> provider_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeData);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_H_