Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/shelf/shelf.h

Index: ash/shelf/shelf.h
diff --git a/ash/shelf/shelf.h b/ash/shelf/shelf.h
index 5cc1fed2c84f20606ad574b688373133013cff94..c0e092c253c99f23e4c68d26f39213b04d268553 100644
--- a/ash/shelf/shelf.h
+++ b/ash/shelf/shelf.h
@@ -10,6 +10,7 @@
 #include <memory>
 
 #include "ash/ash_export.h"
+#include "ash/common/shelf/shelf_background_animator_observer.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/shelf_locking_manager.h"
 #include "ash/common/shelf/shelf_types.h"
@@ -49,14 +50,14 @@ class ShelfTestAPI;
 
 // Controller for shelf state. All access to state (visibility, auto-hide, etc.)
 // should occur via this class.
-class ASH_EXPORT Shelf {
+class ASH_EXPORT Shelf : public ShelfBackgroundAnimatorObserver {

[James Cook, 2016/07/27 00:30:39]

Can the ShelfBackgroundAnimatorObserver live somewhere other than on Shelf?
Maybe on ShelfView, or ShelfWidget, or failing that WmShelf? I'm trying to get
rid of Shelf.

[bruthig, 2016/07/27 17:05:45]

I made the ShelfView extend the ShelfBackgroundAnimatorObserver and passed the
ShelfBackgroundAnimator owned by the ShelfWidget to the ShelfView so that the
ShelfView can add/remove itself as an observer.

PTAL

  public:
   static const char kNativeViewName[];
 
   Shelf(ShelfModel* model,
         WmShelf* wm_shelf,
         ShelfWidget* widget);
-  virtual ~Shelf();
+  ~Shelf() override;
 
   // 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 +153,9 @@ class ASH_EXPORT Shelf {
   // Returns ApplicationDragAndDropHost for this shelf.
   app_list::ApplicationDragAndDropHost* GetDragAndDropHostForAppList();
 
+  // ShelfBackgroundAnimatorObserver:
+  void UpdateShelfItemBackground(int alpha) override;
+
   ShelfLockingManager* shelf_locking_manager_for_testing() {
     return &shelf_locking_manager_;
   }