Remove the unmaintained performance monitor.

chrome/browser/chrome_notification_types.h

 // Copyright 2012 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 CHROME_BROWSER_CHROME_NOTIFICATION_TYPES_H_
 #define CHROME_BROWSER_CHROME_NOTIFICATION_TYPES_H_
 
 #include "build/build_config.h"
 #include "extensions/browser/notification_types.h"
 
@@ skipping 442 matching lines @@
   // Download Notifications --------------------------------------------------
 
   // Sent when a download is initiated. It is possible that the download will
   // not actually begin due to the DownloadRequestLimiter cancelling it
   // prematurely.
   // The source is the corresponding RenderViewHost. There are no details.
   NOTIFICATION_DOWNLOAD_INITIATED,
 
   // Misc --------------------------------------------------------------------
 
-  // Sent when PerformanceMonitor has finished all the initial steps of data
-  // collection and has begun passively observing. The source is the
-  // PerformanceMonitor*. No details are expected.
-  NOTIFICATION_PERFORMANCE_MONITOR_INITIALIZED,
-
 #if defined(OS_CHROMEOS)
   // Sent when a chromium os user logs in.
   // The details are a chromeos::User object.
   NOTIFICATION_LOGIN_USER_CHANGED,
 
   // Sent immediately after the logged-in user's profile is ready.
   // The details are a Profile object.
   NOTIFICATION_LOGIN_USER_PROFILE_PREPARED,
 
   // Sent when the chromium session of a particular user is started.
@@ skipping 219 matching lines @@
   // Note:-
   // Currently only Content and Chrome define and use notifications.
   // Custom notifications not belonging to Content and Chrome should start
   // from here.
   NOTIFICATION_CHROME_END,
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_CHROME_NOTIFICATION_TYPES_H_