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

ui/base/dragdrop/os_exchange_data.h

Index: ui/base/dragdrop/os_exchange_data.h
===================================================================
--- ui/base/dragdrop/os_exchange_data.h	(revision 134125)
+++ ui/base/dragdrop/os_exchange_data.h	(working copy)
@@ -50,7 +50,7 @@
  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;