Remove unused notification kTabModelUserNavigatedNavigation.

ios/chrome/browser/tabs/tab_model.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 IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_
 #define IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_
 
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
@@ skipping 20 matching lines @@
 class WebState;
 }
 
 // A list of notifications about changes in the model or changes in tab
 // state.
 
 // A tab is about to load a URL. The tab in question is in the userInfo under
 // kTabModelTabKey. This may fire multiple times during a load, for example, on
 // redirects.
 extern NSString* const kTabModelTabWillStartLoadingNotification;
-// Notification sent when user navigates away from the current page.
-extern NSString* const kTabModelUserNavigatedNotification;
 // A tab started to load a URL. The tab in question is in the userInfo under
 // kTabModelTabKey.
 extern NSString* const kTabModelTabDidStartLoadingNotification;
 // A tab finished loading a URL. The tab in question is in the userInfo under
 // kTabModelTabKey.
 extern NSString* const kTabModelTabDidFinishLoadingNotification;
 // All tabs have finished their shutdown sequences.
 // NOTE: This notification is not sent when closing a single tab that happens
 // to be the last tab.
 extern NSString* const kTabModelAllTabsDidCloseNotification;
@@ skipping 225 matching lines @@
 // Called by the Tab to inform its parent that it has been closed.
 - (void)didCloseTab:(Tab*)closedTab;
 // Called by |tab| to inform the model that a navigation has taken place.
 // TODO(crbug.com/661983): once more of the navigation state has moved into WC,
 // replace this with WebStateObserver.
 - (void)navigationCommittedInTab:(Tab*)tab;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_