Add MD ink drop ripple to shelf app items

ash/shelf/ink_drop_button_listener.h

Index: ash/shelf/ink_drop_button_listener.h
diff --git a/ash/shelf/ink_drop_button_listener.h b/ash/shelf/ink_drop_button_listener.h
new file mode 100644
index 0000000000000000000000000000000000000000..554a759b2259b4f4956f22856f4efa0ebd31d87f
--- /dev/null
+++ b/ash/shelf/ink_drop_button_listener.h
@@ -0,0 +1,40 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_SHELF_INK_DROP_BUTTON_LISTENER_H_
+#define ASH_SHELF_INK_DROP_BUTTON_LISTENER_H_
+
+#include "ash/ash_export.h"
+
+namespace views {
+class Button;
+class InkDrop;
+}
+
+namespace ash {
+
+// An interface used by buttons on shelf to notify ShelfView when they are
+// pressed. |ink_drop| is used to do appropriate ink drop animation based on the
+// action performed.
+// TODO(mohsen): A better approach would be to return a value indicating the
+// type of action performed such that the button can animate the ink drop.
+// Currently, it is not possible because showing menu is synchronous and blocks
+// the call. Fix this after menu is converted to synchronous.  Long-term, the
+// return value can be merged into ButtonListener.
+class ASH_EXPORT InkDropButtonListener {
+ public:
+  virtual void ButtonPressed(views::Button* sender,
+                             const ui::Event& event,
+                             views::InkDrop* ink_drop) = 0;
+
+ protected:
+  InkDropButtonListener() {}
+  virtual ~InkDropButtonListener() {}
+
+  DISALLOW_COPY_AND_ASSIGN(InkDropButtonListener);

[James Cook, 2016/06/14 16:34:28]

nit: You don't need this if you have a pure virtual method. Nor do you need the
constructor.

[mohsen, 2016/06/14 20:40:30]

Done.

+};
+
+}  // namespace ash
+
+#endif  // ASH_SHELF_INK_DROP_BUTTON_LISTENER_H_