Linux Aura: Use managed tab dragging when possible (Reland)

ui/wm/public/window_move_client.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_WM_PUBLIC_WINDOW_MOVE_CLIENT_H_
 #define UI_WM_PUBLIC_WINDOW_MOVE_CLIENT_H_
 
 #include "ui/aura/aura_export.h"
 #include "ui/gfx/geometry/vector2d.h"
 
@@ skipping 23 matching lines @@
   // offset from the window origin to the cursor when the drag was started.
   // Returns MOVE_SUCCESSFUL if the move has completed successfully, or
   // MOVE_CANCELED otherwise.
   virtual WindowMoveResult RunMoveLoop(Window* window,
                                        const gfx::Vector2d& drag_offset,
                                        WindowMoveSource source) = 0;
 
   // Ends a previously started move loop.
   virtual void EndMoveLoop() = 0;
 
- protected:

[Tom (Use chromium acct), 2016/10/12 00:55:19]

I needed to do this because DesktopWindowTreeHostX11 now keeps a unique_pointer
to a WindowMoveClient

   virtual ~WindowMoveClient() {}
 };
 
 // Sets/Gets the activation client for the specified window.
 AURA_EXPORT void SetWindowMoveClient(Window* window,
                                      WindowMoveClient* client);
 AURA_EXPORT WindowMoveClient* GetWindowMoveClient(Window* window);
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_WM_PUBLIC_WINDOW_MOVE_CLIENT_H_