mac: Fix a dangling delegate bug with MCPopupController.

ui/message_center/cocoa/popup_controller.h

 // Copyright (c) 2013 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_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_
 #define UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <string>
@@ skipping 28 matching lines @@
   // If the swipe-away gesture received NSEventPhaseEnded.
   BOOL swipeGestureEnded_;
 
   // The frame of the popup before any swipe animation started. Used to
   // calculate the animating position of the window when swiping away.
   NSRect originalFrame_;
 
   // Is the popup currently being closed?
   BOOL isClosing_;
 
+#ifndef NDEBUG
+  // Has the popup been closed before being dealloc-ed.
+  BOOL hasBeenClosed_;
+#endif
+
   // The current bounds of the popup frame if no animation is playing.
   // Otherwise, it is the target bounds of the popup frame.
   NSRect bounds_;
 
   // Used to play animation when the popup shows, changes bounds and closes.
   base::scoped_nsobject<NSViewAnimation> boundsAnimation_;
 
   // Used to track the popup for mouse entered and exited events.
   ui::ScopedCrTrackingArea trackingArea_;
 }
@@ skipping 26 matching lines @@
 // Returns the window bounds. This is the target bounds to go to if the bounds
 // animation is playing.
 - (NSRect)bounds;
 
 // Changes the window bounds with animation.
 - (void)setBounds:(NSRect)newBounds;
 
 @end
 
 #endif  // UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_