Add MD ink drop ripple to shelf app items

ash/shelf/app_list_button.cc

Index: ash/shelf/app_list_button.cc
diff --git a/ash/shelf/app_list_button.cc b/ash/shelf/app_list_button.cc
index 51a1a281f5b4b18d212aef46182e831ba46c299a..089f7ec54acddb9b50f0557766aaeb3b02727826 100644
--- a/ash/shelf/app_list_button.cc
+++ b/ash/shelf/app_list_button.cc
@@ -27,7 +27,7 @@
 namespace ash {
 
 AppListButton::AppListButton(ShelfView* shelf_view)
-    : views::ImageButton(shelf_view),
+    : views::ImageButton(nullptr),
       draw_background_as_active_(false),
       shelf_view_(shelf_view) {
   SetAccessibleName(
@@ -165,6 +165,11 @@ void AppListButton::GetAccessibleState(ui::AXViewState* state) {
   state->name = shelf_view_->GetTitleForView(this);
 }
 
+void AppListButton::NotifyClick(const ui::Event& event) {
+  ImageButton::NotifyClick(event);
+  shelf_view_->ButtonPressed(this, event, ink_drop());
+}
+
 void AppListButton::SetDrawBackgroundAsActive(
     bool draw_background_as_active) {
   if (draw_background_as_active_ == draw_background_as_active)