Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

ash/aura/wm_shelf_aura.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/aura/wm_shelf_aura.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shelf/wm_shelf_observer.h"
 #include "ash/common/wm_window.h"
 #include "ash/shelf/shelf.h"
@@ skipping 160 matching lines @@
   return shelf_->shelf_view_for_testing();
 }
 
 void WmShelfAura::WillDeleteShelfLayoutManager() {
   ResetShelfLayoutManager();
 }
 
 void WmShelfAura::OnBackgroundUpdated(
     ShelfBackgroundType background_type,
     BackgroundAnimatorChangeType change_type) {
+  if (background_type == GetBackgroundType())
+    return;
   FOR_EACH_OBSERVER(WmShelfObserver, observers_,
-                    OnBackgroundUpdated(background_type, change_type));
+                    OnBackgroundTypeChanged(background_type, change_type));
 }
 
 void WmShelfAura::WillChangeVisibilityState(ShelfVisibilityState new_state) {
   FOR_EACH_OBSERVER(WmShelfObserver, observers_,
                     WillChangeVisibilityState(new_state));
 }
 
 void WmShelfAura::OnAutoHideStateChanged(ShelfAutoHideState new_state) {
   FOR_EACH_OBSERVER(WmShelfObserver, observers_,
                     OnAutoHideStateChanged(new_state));
 }
 
 void WmShelfAura::OnShelfIconPositionsChanged() {
   FOR_EACH_OBSERVER(WmShelfObserver, observers_, OnShelfIconPositionsChanged());
 }
 
 }  // namespace ash