[Mac][MC] Close the tray window when the user clicks outside it.

ui/message_center/cocoa/tray_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_TRAY_CONTROLLER_H_
 #define UI_MESSAGE_CENTER_COCOA_TRAY_CONTROLLER_H_
 
 #import <AppKit/AppKit.h>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_nsobject.h"
 #include "ui/message_center/message_center_export.h"
 
 @class MCTrayViewController;
 
 namespace message_center {
 class MessageCenterTray;
 }
 
 // The window controller for the message center tray. This merely hosts the
 // view from MCTrayViewController.
 MESSAGE_CENTER_EXPORT
 @interface MCTrayController : NSWindowController<NSWindowDelegate> {
  @private
   message_center::MessageCenterTray* tray_;  // Weak, indirectly owns this.
 
   // View controller that provides this window's content.
   scoped_nsobject<MCTrayViewController> viewController_;
+
+  // An event monitor that listens for clicks outside the tray window to cause
+  // it to close.
+  id clickEventMonitor_;
 }
 
 // Designated initializer.
 - (id)initWithMessageCenterTray:(message_center::MessageCenterTray*)tray;
 
 // Opens the message center tray with the window's upper-left corner at |point|.
 - (void)showTrayAt:(NSPoint)point;
 
 // Callback from MessageCenterTrayDelegate, used to update the tray content.
 - (void)onMessageCenterTrayChanged;
 
 @end
 
 #endif  // UI_MESSAGE_CENTER_COCOA_TRAY_CONTROLLER_H_