Add MD ink drop ripple to app list button

ash/shelf/shelf.h

Index: ash/shelf/shelf.h
diff --git a/ash/shelf/shelf.h b/ash/shelf/shelf.h
index 66c23b266464fd67eda3d362e7b2b7c55a6daf54..9469ed29aa86ed8f600fbeb99f3e7a9e58a1d32b 100644
--- a/ash/shelf/shelf.h
+++ b/ash/shelf/shelf.h
@@ -35,6 +35,7 @@ class View;
 }
 
 namespace ash {
+class AppListButton;
 class FocusCycler;
 class ShelfDelegate;
 class ShelfIconObserver;
@@ -136,7 +137,7 @@ class ASH_EXPORT Shelf {
 
   void SchedulePaint();
 
-  views::View* GetAppListButtonView() const;
+  AppListButton* GetAppListButton() const;
 
   // Launch a 0-indexed shelf item in the shelf.
   // A negative index launches the last shelf item in the shelf.