Cancel drag if display configuration changes.

ui/aura/client/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_AURA_CLIENT_WINDOW_MOVE_CLIENT_H_
 #define UI_AURA_CLIENT_WINDOW_MOVE_CLIENT_H_
 
 #include "ui/aura/aura_export.h"
 
 namespace gfx {
 class Point;
 }
 
 namespace aura {
 class Window;
 namespace client {
 
+enum WindowMoveResult {
+  MOVE_SUCCESSFUL,  // Moving window was successful.
+  MOVE_CANCELED    // Moving window was canceled.
+};
+
 // An interface implemented by an object that manages programatically keyed
 // window moving.
 class AURA_EXPORT WindowMoveClient {
  public:
   // Starts a nested message loop for moving the window. |drag_offset| is the
   // offset from the window origin to the cursor when the drag was started.
-  virtual void RunMoveLoop(Window* window, const gfx::Point& drag_offset) = 0;
+  // Returns MOVE_SUCCESSFUL if the move has completed successfully, or
+  // MOVE_CANCELED otherwise.
+  virtual WindowMoveResult RunMoveLoop(Window* window,
+                                       const gfx::Point& drag_offset) = 0;
 
   // Ends a previously started move loop.
   virtual void EndMoveLoop() = 0;
 
  protected:
   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_AURA_CLIENT_WINDOW_MOVE_CLIENT_H_