[Mac][MC] Allow popup notifications to be dismissed with a swipe gesture.

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>
 
 #import "base/memory/scoped_nsobject.h"
 #include "ui/message_center/message_center_export.h"
 
 namespace message_center {
 class MessageCenter;
 class Notification;
 }
 
 @class MCNotificationController;
 
 // A window controller that hosts a notification as a popup balloon on the
 // user's desktop. Unlike most window controllers, this does not own itself and
 // its lifetime must be managed manually.
 MESSAGE_CENTER_EXPORT
 @interface MCPopupController : NSWindowController {
  @private
+  // Global message center. Weak.
+  message_center::MessageCenter* messageCenter_;
+
+  // The view controller that provide's the popup content view.
   scoped_nsobject<MCNotificationController> notificationController_;
+
+  // 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_;
 }
 
 // Designated initializer.
 - (id)initWithNotification:(const message_center::Notification*)notification
     messageCenter:(message_center::MessageCenter*)messageCenter;
 
 // Accessor for the view controller.
 - (MCNotificationController*)notificationController;
 
 // Accessor for the notification model object.
 - (const message_center::Notification*)notification;
 
 // Gets the notification ID. This string is owned by the NotificationController
 // rather than the model object, so it's safe to use after the Notification has
 // been deleted.
 - (const std::string&)notificationID;
 
 @end
 
 #endif  // UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_