Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

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 when balloon notifications are removed
-// completely.
-bool IsRichNotificationEnabled() {
-#if defined(OS_MACOSX) || defined(USE_AURA)
-  return true;
-#else
-  return false;
-#endif
-}
-
 MessageCenterShowState GetMessageCenterShowState() {
 #if defined(OS_MACOSX)
   std::string tray_behavior =
       CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kNotificationCenterTrayBehavior);
   if (tray_behavior == "never")
     return MESSAGE_CENTER_SHOW_NEVER;
   if (tray_behavior == "always")
     return MESSAGE_CENTER_SHOW_ALWAYS;
   if (tray_behavior == "unread")
     return MESSAGE_CENTER_SHOW_UNREAD;
   return MESSAGE_CENTER_SHOW_AFTER_FIRST;
 #elif defined(OS_CHROMEOS)
   return MESSAGE_CENTER_SHOW_UNREAD;
 #else  // defined(OS_WIN) || defined(OS_LINUX)
   return MESSAGE_CENTER_SHOW_AFTER_FIRST;
 #endif
 }
 
 }  // namespace message_center