Implement TOGGLE_EXPANSION action for the ARC notifications.

ui/arc/notification/arc_notification_item.h

 // Copyright 2016 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_ARC_NOTIFICATION_ARC_NOTIFICATION_ITEM_H_
 #define UI_ARC_NOTIFICATION_ARC_NOTIFICATION_ITEM_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 22 matching lines @@
 
   // Methods called from ArcNotificationManager:
   void OnClosedFromAndroid();
 
   // Methods called from ArcNotificationItemDelegate:
   void Close(bool by_user);
   void Click();
   void ButtonClick(int button_index);
   void OpenSettings();
   bool IsOpeningSettingsSupported() const;
+  void ToggleExpansion();
 
   const std::string& notification_key() const { return notification_key_; }
 
  protected:
   static int ConvertAndroidPriority(int android_priority);
 
   // Checks whether there is on-going |notification_|.
   bool HasPendingNotification();
   // Cache the |data| in |newer_data_|.
   void CacheArcNotificationData(mojom::ArcNotificationDataPtr data);
@@ skipping 45 matching lines @@
 
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<ArcNotificationItem> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcNotificationItem);
 };
 
 }  // namespace arc
 
 #endif  // UI_ARC_NOTIFICATION_ARC_NOTIFICATION_ITEM_H_