Attemp 2 at:

chrome/common/notification_type.h

 // Copyright (c) 2010 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_COMMON_NOTIFICATION_TYPE_H_
 #define CHROME_COMMON_NOTIFICATION_TYPE_H_
 
 // This file describes various types used to describe and filter notifications
 // that pass through the NotificationService.
 //
@@ skipping 857 matching lines @@
 
     // Sent when an omnibox extension has sent back omnibox suggestions. The
     // source is the profile, and the details are an ExtensionOmniboxSuggestions
     // object.
     EXTENSION_OMNIBOX_SUGGESTIONS_READY,
 
     // Sent when the user accepts the input in an extension omnibox keyword
     // session. The source is the profile.
     EXTENSION_OMNIBOX_INPUT_ENTERED,
 
-    // The source is the extension object that changed. Details is a bool*
-    // with the new visibility.
-    EXTENSION_APP_TOOLBAR_VISIBILITY_CHANGED,
-
     // Debugging ---------------------------------------------------------------
 
     // TODO(mpcomplete): Sent to diagnose a bug. Remove when fixed.
     // http://code.google.com/p/chromium/issues/detail?id=21201
     EXTENSION_PORT_DELETED_DEBUG,
 
     // Desktop Notifications ---------------------------------------------------
 
     // This notification is sent when a balloon is connected to a renderer
     // process to render the balloon contents.  The source is a
@@ skipping 211 matching lines @@
 };
 
 inline bool operator==(NotificationType::Type a, NotificationType b) {
   return a == b.value;
 }
 inline bool operator!=(NotificationType::Type a, NotificationType b) {
   return a != b.value;
 }
 
 #endif  // CHROME_COMMON_NOTIFICATION_TYPE_H_