Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/shelf/shelf_view.h

Index: ash/shelf/shelf_view.h
diff --git a/ash/shelf/shelf_view.h b/ash/shelf/shelf_view.h
index 0bbc33470c88040b827d5d3158aa884e1e42ed92..13db5412afe8b36f4b14f06b3350396e964c0b48 100644
--- a/ash/shelf/shelf_view.h
+++ b/ash/shelf/shelf_view.h
@@ -158,6 +158,9 @@ class ASH_EXPORT ShelfView : public views::View,
                                Pointer pointer,
                                bool canceled);
 
+  // Updates all shelf item backgrounds.
+  void UpdateShelfItemBackground(int alpha);
+
   // Return the view model for test purposes.
   const views::ViewModel* view_model_for_test() const {
     return view_model_.get();