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

ui/message_center/message_center_util.h

 // 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.
 
 #ifndef UI_MESSAGE_CENTER_MESSAGE_CENTER_UTIL_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_UTIL_H_
 
 #include "ui/message_center/message_center_export.h"
 
 namespace message_center {
 
-MESSAGE_CENTER_EXPORT bool IsRichNotificationEnabled();
-
-// If Rich Notificaitons are enabled by default on a platform, run the
-// corresponding tests on that platform.
-#if defined(OS_WIN) || defined(USE_AURA) || defined(OS_MACOSX)
-#define RUN_MESSAGE_CENTER_TESTS 1
-#endif
-
 enum MessageCenterShowState {
   MESSAGE_CENTER_SHOW_NEVER = 0,
   MESSAGE_CENTER_SHOW_UNREAD,
   MESSAGE_CENTER_SHOW_AFTER_FIRST,
   MESSAGE_CENTER_SHOW_ALWAYS
 };
 
 MESSAGE_CENTER_EXPORT MessageCenterShowState GetMessageCenterShowState();
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_UTIL_H_