Add ripple effect to action in expand button.

ui/message_center/views/notification_header_view.h

Index: ui/message_center/views/notification_header_view.h
diff --git a/ui/message_center/views/notification_header_view.h b/ui/message_center/views/notification_header_view.h
index addc8d195b7ef56831b0624d93f99208972d973e..f32e7fd6ce39e71c0c5db48428e14373a0dc2f9a 100644
--- a/ui/message_center/views/notification_header_view.h
+++ b/ui/message_center/views/notification_header_view.h
@@ -17,8 +17,14 @@ class Label;
 
 namespace message_center {
 
+namespace {
+class ExpandButton;

[yoshiki, 2017/07/03 06:15:47]

We should avoid forward declaring a methods in  anonymous namespace. Could you
make it a child-class of NotificationHeaderView, or make it non-friend?

[tetsui, 2017/07/03 07:10:54]

Done.

+}
+
 class NotificationHeaderView : public views::CustomButton {
  public:
+  friend class ExpandButton;
+
   NotificationHeaderView(views::ButtonListener* listener);
   void SetAppIcon(const gfx::ImageSkia& img);
   void SetAppName(const base::string16& name);