Add MD ink drop ripple to app list button

ash/shelf/shelf.cc

Index: ash/shelf/shelf.cc
diff --git a/ash/shelf/shelf.cc b/ash/shelf/shelf.cc
index 358badd6739f5d43e4b8d9321b7ae54e85d3975d..2176db2a8ab99b3e24bc0b80306d12d729947769 100644
--- a/ash/shelf/shelf.cc
+++ b/ash/shelf/shelf.cc
@@ -180,8 +180,8 @@ void Shelf::SchedulePaint() {
   shelf_view_->SchedulePaintForAllButtons();
 }
 
-views::View* Shelf::GetAppListButtonView() const {
-  return shelf_view_->GetAppListButtonView();
+AppListButton* Shelf::GetAppListButton() const {
+  return shelf_view_->GetAppListButton();
 }
 
 void Shelf::LaunchAppIndexAt(int item_index) {