Made --enable-rich-notifications flag available to message_center.

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 a11060241480288a3969296fa97113187ebc32c0..6c5c7f4cd33cbabb1ef20e6f06c38b51eb9b3ee0 100644
--- a/ui/message_center/message_center_switches.cc
+++ b/ui/message_center/message_center_switches.cc
@@ -10,5 +10,9 @@ namespace switches {
 const char kDisableNewMessageCenterBubble[] =
     "disable-new-message-center-bubble";
 
+const char kEnableRichNotifications[] = "enable-rich-notifications";
+
+const char kEnableNewSimpleNotifications[] = "enable-new-simple-notifications";
+
 }  // namespace switches
 }  // namespace message_center