Remove TopSites notification in favor of Observers

chrome/browser/history/top_sites.h

 // Copyright (c) 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_HISTORY_TOP_SITES_H_
 #define CHROME_BROWSER_HISTORY_TOP_SITES_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
@@ skipping 165 matching lines @@
 
   // Remove Observer from the list.
   void RemoveObserver(TopSitesObserver* observer);
 
  protected:
   void NotifyTopSitesLoaded();
   void NotifyTopSitesChanged();
   ~TopSites() override;
 
  private:
-  ObserverList<TopSitesObserver> observer_list_;
+  ObserverList<TopSitesObserver, true> observer_list_;
   friend class base::RefCountedThreadSafe<TopSites>;
 };
 
 #if defined(OS_ANDROID)
 const int kPrepopulatedPagesCount = 0;
 #else
 const int kPrepopulatedPagesCount = 2;
 #endif
 extern const TopSites::PrepopulatedPage
     kPrepopulatedPages[kPrepopulatedPagesCount];
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_TOP_SITES_H_