[ash-md] Wired in the Shelf color to be derived from the Wallpaper.

ash/common/shelf/shelf_widget.h

 // Copyright (c) 2012 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.
 
 #ifndef ASH_COMMON_SHELF_SHELF_WIDGET_H_
 #define ASH_COMMON_SHELF_SHELF_WIDGET_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 78 matching lines @@
   // Returns the button that opens the app launcher.
   AppListButton* GetAppListButton() const;
 
   // Returns the ApplicationDragAndDropHost for this shelf.
   app_list::ApplicationDragAndDropHost* GetDragAndDropHostForAppList();
 
   // Overridden from views::WidgetObserver:
   void OnWidgetActivationChanged(views::Widget* widget, bool active) override;
 
   // ShelfBackgroundAnimatorObserver overrides:
-  void UpdateShelfItemBackground(int alpha) override;
+  void UpdateShelfItemBackground(SkColor color) override;
 
   // ShelfLayoutManagerObserver overrides:
   void WillDeleteShelfLayoutManager() override;
 
  private:
   class DelegateView;
   friend class DelegateView;
 
   WmShelf* wm_shelf_;
 
@@ skipping 11 matching lines @@
   ShelfView* shelf_view_;
   ShelfBackgroundAnimator background_animator_;
   bool activating_as_fallback_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfWidget);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_SHELF_WIDGET_H_