Initial implementation of new-style notification

ui/message_center/message_center_switches.cc

Index: ui/message_center/message_center_switches.cc
diff --git a/ui/message_center/message_center_switches.cc b/ui/message_center/message_center_switches.cc
index 4caba23fe8cbfeca1ed152e3883ba9aa0fd4e698..05b4862d5406907355d1f2213ff936eeadaca566 100644
--- a/ui/message_center/message_center_switches.cc
+++ b/ui/message_center/message_center_switches.cc
@@ -17,4 +17,11 @@ const char kEnableMessageCenterAlwaysScrollUpUponNotificationRemoval[] =
 const char kMessageCenterChangesWhileOpen[] =
     "message-center-changes-while-open";
 
+// Flag to enable or disable new-style notification. This flag will be removed
+// once the feature gets stable.
+const char kMessageCenterNewStyleNotification[] =
+    "message-center-new-style-notification";
+const char kMessageCenterNewStyleNotificationEnabled[] = "enabled";
+const char kMessageCenterNewStyleNotificationDisabled[] = "disabled";
+
 }  // namespace switches