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

ash/shelf/shelf.h

Index: ash/shelf/shelf.h
diff --git a/ash/shelf/shelf.h b/ash/shelf/shelf.h
index 4d85bb0fd9a53505a8b36b2a5a0862abdf1e6455..497c2b5490760afb722ce58f90219c4eb210a454 100644
--- a/ash/shelf/shelf.h
+++ b/ash/shelf/shelf.h
@@ -56,7 +56,7 @@ class ASH_EXPORT Shelf {
   Shelf(ShelfModel* model,
         WmShelf* wm_shelf,
         ShelfWidget* widget);
-  virtual ~Shelf();
+  ~Shelf();
 
   // Return the shelf for the primary display. NULL if no user is logged in yet.
   // Useful for tests. For production code use ForWindow() because the user may
@@ -152,6 +152,9 @@ class ASH_EXPORT Shelf {
   // Returns ApplicationDragAndDropHost for this shelf.
   app_list::ApplicationDragAndDropHost* GetDragAndDropHostForAppList();
 
+  // Updates the background for the shelf items.
+  void UpdateShelfItemBackground(int alpha);
+
   ShelfLockingManager* shelf_locking_manager_for_testing() {
     return &shelf_locking_manager_;
   }