Extend notifications.mojom for expandable notifications.

ui/arc/notification/arc_custom_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_CUSTOM_NOTIFICATION_ITEM_H_
 #define UI_ARC_NOTIFICATION_ARC_CUSTOM_NOTIFICATION_ITEM_H_
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "ui/arc/notification/arc_notification_item.h"
@@ skipping 32 matching lines @@
   // Increment |window_ref_count_| and a CreateNotificationWindow request
   // is sent when |window_ref_count_| goes from zero to one.
   void IncrementWindowRefCount();
 
   // Decrement |window_ref_count_| and a CloseNotificationWindow request
   // is sent when |window_ref_count_| goes from one to zero.
   void DecrementWindowRefCount();
 
   bool pinned() const { return pinned_; }
   const gfx::ImageSkia& snapshot() const { return snapshot_; }
+  mojom::ArcNotificationExpandState expand_state() const {
+    return expand_state_;
+  }
 
  private:
   bool pinned_ = false;
+  mojom::ArcNotificationExpandState expand_state_ =
+      mojom::ArcNotificationExpandState::FIXED_SIZE;
   gfx::ImageSkia snapshot_;
   int window_ref_count_ = 0;
 
   base::ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcCustomNotificationItem);
 };
 
 }  // namespace arc
 
 #endif  // UI_ARC_NOTIFICATION_ARC_CUSTOM_NOTIFICATION_ITEM_H_