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

ash/common/shelf/app_list_button.h

Index: ash/common/shelf/app_list_button.h
diff --git a/ash/common/shelf/app_list_button.h b/ash/common/shelf/app_list_button.h
index 79460cc6f11279db9bd431d9eb1dda5ea574cf75..e6d55bf182ebe03d9b56d1c4a6e2e144c14aa9d6 100644
--- a/ash/common/shelf/app_list_button.h
+++ b/ash/common/shelf/app_list_button.h
@@ -7,6 +7,7 @@
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
+#include "third_party/skia/include/core/SkColor.h"
 #include "ui/views/controls/button/image_button.h"
 
 namespace ash {
@@ -29,8 +30,8 @@ class ASH_EXPORT AppListButton : public views::ImageButton {
 
   bool draw_background_as_active() const { return draw_background_as_active_; }
 
-  // Sets alpha value of the background and schedules a paint.
-  void SetBackgroundAlpha(int alpha);
+  // Updates background and schedules a paint.
+  void UpdateShelfItemBackground(SkColor color);
 
  protected:
   // views::ImageButton overrides:
@@ -73,8 +74,8 @@ class ASH_EXPORT AppListButton : public views::ImageButton {
   // the application list.
   bool draw_background_as_active_;
 
-  // Alpha value used to paint the background.
-  int background_alpha_;
+  // Color used to paint the background.
+  SkColor background_color_;
 
   InkDropButtonListener* listener_;
   ShelfView* shelf_view_;