Remove OTIFICATION_METRIC_EVENT_DURATION that no-one is observing

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"
 
 #if defined(ENABLE_EXTENSIONS)
@@ skipping 124 matching lines @@
   // the InfoBarService the InfoBar was added to.  The details is a
   // Details<InfoBar::AddedDetails>.
   NOTIFICATION_TAB_CONTENTS_INFOBAR_ADDED,
 
   // This message is sent when an InfoBar is about to be removed from an
   // InfoBarService.  The source is a Source<InfoBarService> with a pointer to
   // the InfoBarService the InfoBar was removed from.  The details is a
   // Details<InfoBar::RemovedDetails>.
   NOTIFICATION_TAB_CONTENTS_INFOBAR_REMOVED,
 
-  // Used to fire notifications about how long various events took to
-  // complete.  E.g., this is used to get more fine grained timings from the
-  // new tab page.  The source is a WebContents and the details is a
-  // MetricEventDurationDetails.
-  NOTIFICATION_METRIC_EVENT_DURATION,
-
 #if defined(ENABLE_EXTENSIONS)
   // This notification is sent when extensions::TabHelper::SetExtensionApp is
   // invoked. The source is the extensions::TabHelper SetExtensionApp was
   // invoked on.
   NOTIFICATION_TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED,
 #endif
 
   // Tabs --------------------------------------------------------------------
 
   // Sent when a tab is added to a WebContentsDelegate. The source is the
@@ skipping 528 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_