Add MD ink drop ripple to app list button

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 6676f29fabacfe309cbedc2d859fb5e4b6d4f5a9..fd04a375db8667a1262e45215ea9f2ed2e2ddb1b 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -245,6 +245,10 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   // Shows the app list if it's not visible. Dismisses it otherwise.
   void ToggleAppList(aura::Window* anchor);
 
+  // Returns app list actual visibility. This might differ from
+  // GetAppListTargetVisibility() when hiding animation is still in flight.
+  bool IsApplistVisible() const;
+
   // Returns app list target visibility.
   bool GetAppListTargetVisibility() const;