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 8aed464df31f2ceabfcf3586b011ddf0b009a971..bb3a16c6a1b738988cf7f6f1fb97bd3680fafc63 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -248,6 +248,10 @@ 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;