Extract the view of control buttons on notification into a separated class

ui/arc/notification/arc_notification_delegate.cc

Index: ui/arc/notification/arc_notification_delegate.cc
diff --git a/ui/arc/notification/arc_notification_delegate.cc b/ui/arc/notification/arc_notification_delegate.cc
index 8035e6110731ff5c1769c8f5b031eb3367234493..fae1302c1881d98c573d64be885462bdbcec2929 100644
--- a/ui/arc/notification/arc_notification_delegate.cc
+++ b/ui/arc/notification/arc_notification_delegate.cc
@@ -45,4 +45,10 @@ void ArcNotificationDelegate::Click() {
   item_->Click();
 }
 
+bool ArcNotificationDelegate::SettingsClick() {
+  DCHECK(item_);
+  item_->OpenSettings();
+  return true;
+}
+
 }  // namespace arc