Start PopularSites fetch from separate function.

chrome/browser/android/ntp/most_visited_sites_bridge.h

 // Copyright 2016 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_ANDROID_NTP_MOST_VISITED_SITES_BRIDGE_H_
 #define CHROME_BROWSER_ANDROID_NTP_MOST_VISITED_SITES_BRIDGE_H_
 
 #include <jni.h>
 #include <stddef.h>
 
@@ skipping 63 matching lines @@
     void OnURLFilterChanged() override;
 
    private:
     Profile* const profile_;
     Observer* supervisor_observer_;
     ScopedObserver<SupervisedUserService, SupervisedUserServiceObserver>
         register_observer_;
   };
   SupervisorBridge supervisor_;
 
+  ntp_tiles::PopularSites popular_sites_;
   ntp_tiles::MostVisitedSites most_visited_;
 
   DISALLOW_COPY_AND_ASSIGN(MostVisitedSitesBridge);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_NTP_MOST_VISITED_SITES_BRIDGE_H_