mash: Use the new mus drag and drop API to get drag working in mash.

services/ui/public/cpp/window.h

 // Copyright 2014 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 SERVICES_UI_PUBLIC_CPP_WINDOW_H_
 #define SERVICES_UI_PUBLIC_CPP_WINDOW_H_
 
 #include <stdint.h>
 #include <vector>
 
@@ skipping 221 matching lines @@
 
   // TODO(sky): this API is only applicable to the WindowManager. Move it
   // to a better place.
   void RequestClose();
 
   // Starts an inter-process drag and drop operation. When this finishes, will
   // return the tuple [success, action_taken] to |callback|, where action_taken
   // is one of the ui::mojom::kDropEffect constants in
   // window_tree_constants.mojom.
   void PerformDragDrop(
-      int drag_pointer,
       const std::map<std::string, std::vector<uint8_t>>& drag_data,
       int drag_operation,
       const gfx::Point& cursor_location,
       const SkBitmap& bitmap,
       const base::Callback<void(bool, uint32_t)>& callback);
 
   // Cancels the in progress drag started with PerformDragDrop().
   void CancelDragDrop();
 
   // Tells the window manager to take control of moving the window. Returns
@@ skipping 139 matching lines @@
   };
 
   std::map<const void*, Value> prop_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_H_