Support dragging a virtual file out of the browser.

base/message_pump_win.h

 // Copyright (c) 2006-2008 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 BASE_MESSAGE_PUMP_WIN_H_
 #define BASE_MESSAGE_PUMP_WIN_H_
 
 #include <windows.h>
 
 #include <list>
@@ skipping 139 matching lines @@
 // is peeked, and before a replacement kMsgHaveWork is posted).
 //
 // NOTE: Although it may seem odd that messages are used to start and stop this
 // flow (as opposed to signaling objects, etc.), it should be understood that
 // the native message pump will *only* respond to messages.  As a result, it is
 // an excellent choice.  It is also helpful that the starter messages that are
 // placed in the queue when new task arrive also awakens DoRunLoop.
 //
 class MessagePumpForUI : public MessagePumpWin {
  public:
+  // The application-defined code passed to the hook procedure.
+  static const int kMessageFilterCode = 0x5001;
+
   MessagePumpForUI();
   virtual ~MessagePumpForUI();
 
   // MessagePump methods:
   virtual void ScheduleWork();
   virtual void ScheduleDelayedWork(const Time& delayed_work_time);
 
   // Applications can call this to encourage us to process all pending WM_PAINT
   // messages.  This method will process all paint messages the Windows Message
   // queue can provide, up to some fixed number (to avoid any infinite loops).
@@ skipping 164 matching lines @@
   // The completion port associated with this thread.
   ScopedHandle port_;
   // This list will be empty almost always. It stores IO completions that have
   // not been delivered yet because somebody was doing cleanup.
   std::list<IOItem> completed_io_;
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_WIN_H_