Remove the "Enable Rich Notifications" flag on ChromeOS.

ui/message_center/message_center_util.cc

 // Copyright (c) 2013 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.
 
 #include "ui/message_center/message_center_util.h"
 
 #include "base/command_line.h"
 #include "ui/message_center/message_center_switches.h"
 
 namespace message_center {
 
 // TODO(dimich): remove this function and the kEnableRichNotifications flag
 // when a time period in Canary indicates the new notifications are acceptable
 // for default behavior.
 bool IsRichNotificationEnabled() {
-#if !defined(OS_WIN) && !defined(OS_MACOSX) && !defined(USE_AURA)
+#if defined(OS_CHROMEOS)
+  return true;
+#elif !defined(OS_WIN) && !defined(OS_MACOSX) && !defined(USE_AURA)
   return false;
 #endif
 
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableRichNotifications)) {
     return false;
   }
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableRichNotifications)) {
     return true;
   }
 
   return true;
 }
 
 }  // namespace message_center