Avoid changing |drag_reverted_| if the drag was already completed on ChromeOS

ash/wm/toplevel_window_event_handler.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 ASH_WM_TOPLEVEL_WINDOW_EVENT_HANDLER_H_
 #define ASH_WM_TOPLEVEL_WINDOW_EVENT_HANDLER_H_
 
 #include <set>
 
 #include "ash/ash_export.h"
@@ skipping 40 matching lines @@
   virtual void EndMoveLoop() OVERRIDE;
 
   // Overridden form ash::DisplayController::Observer:
   virtual void OnDisplayConfigurationChanging() OVERRIDE;
 
  private:
   class ScopedWindowResizer;
 
   enum DragCompletionStatus {
     DRAG_COMPLETE,
-    DRAG_REVERT
+    DRAG_REVERT,
+
+    // To be used when WindowResizer::GetTarget() is destroyed. Neither
+    // completes nor reverts the drag because both access the WindowResizer's
+    // window.
+    DRAG_RESIZER_WINDOW_DESTROYED
   };
 
   // Attempts to start a drag if one is not already in progress. Returns true if
   // successful.
   bool AttemptToStartDrag(aura::Window* window,
                           const gfx::Point& point_in_parent,
                           int window_component,
                           aura::client::WindowMoveSource source);
 
-  // Finishes the drag.
-  void CompleteDrag(DragCompletionStatus status);
+  // Completes or reverts the drag if one is in progress. Returns true if a
+  // drag was completed or reverted.
+  bool CompleteDrag(DragCompletionStatus status);
 
   void HandleMousePressed(aura::Window* target, ui::MouseEvent* event);
   void HandleMouseReleased(aura::Window* target, ui::MouseEvent* event);
 
   // Called during a drag to resize/position the window.
   void HandleDrag(aura::Window* target, ui::LocatedEvent* event);
 
   // Called during mouse moves to update window resize shadows.
   void HandleMouseMoved(aura::Window* target, ui::LocatedEvent* event);
 
@@ skipping 33 matching lines @@
   // Used to track if this object is deleted while running a nested message
   // loop. If non-null the destructor sets this to true.
   bool* destroyed_;
 
   DISALLOW_COPY_AND_ASSIGN(ToplevelWindowEventHandler);
 };
 
 }  // namespace aura
 
 #endif  // ASH_WM_TOPLEVEL_WINDOW_EVENT_HANDLER_H_