[ash-md] Remove the number of animators used for the Shelf animations.

ash/common/shelf/wm_shelf.cc

 // 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.
 
 #include "ash/common/shelf/wm_shelf.h"
 
 #include "ash/common/shelf/shelf_controller.h"
 #include "ash/common/shelf/shelf_delegate.h"
 #include "ash/common/shelf/shelf_item_delegate.h"
 #include "ash/common/shelf/shelf_layout_manager.h"
@@ skipping 355 matching lines @@
         base::MakeUnique<AutoHideEventHandler>(shelf_layout_manager());
   }
 }
 
 void WmShelf::OnAutoHideStateChanged(ShelfAutoHideState new_state) {
   for (auto& observer : observers_)
     observer.OnAutoHideStateChanged(new_state);
 }
 
 void WmShelf::OnBackgroundUpdated(ShelfBackgroundType background_type,
-                                  BackgroundAnimatorChangeType change_type) {
+                                  AnimationChangeType change_type) {
   if (background_type == GetBackgroundType())
     return;
   for (auto& observer : observers_)
     observer.OnBackgroundTypeChanged(background_type, change_type);
 }
 
 }  // namespace ash