ntp_tiles: Avoid redundant calls to TopSites

components/ntp_tiles/most_visited_sites.h

 // Copyright 2013 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 COMPONENTS_NTP_TILES_MOST_VISITED_SITES_H_
 #define COMPONENTS_NTP_TILES_MOST_VISITED_SITES_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 175 matching lines @@
       suggestions_subscription_;
 
   ScopedObserver<history::TopSites, history::TopSitesObserver>
       top_sites_observer_;
 
   // The main source of personal tiles - either TOP_SITES or SUGGESTIONS_SEVICE.
   NTPTileSource mv_source_;
 
   NTPTilesVector current_tiles_;
 
-  // For callbacks may be run after destruction.
-  base::WeakPtrFactory<MostVisitedSites> weak_ptr_factory_;
+  // For callbacks may be run after destruction, used exclusively for TopSites
+  // (since it's used to detect whether there's a query in flight).
+  base::WeakPtrFactory<MostVisitedSites> top_sites_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MostVisitedSites);
 };
 
 }  // namespace ntp_tiles
 
 #endif  // COMPONENTS_NTP_TILES_MOST_VISITED_SITES_H_