Add request throttler to thumbnail fetching for articles on mobile NTP

components/ntp_snippets/ntp_snippets_fetcher.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 COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_FETCHER_H_
 #define COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_FETCHER_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 78 matching lines @@
   void SetCallback(const SnippetsAvailableCallback& callback);
 
   // Fetches snippets from the server. |hosts| restricts the results to a set of
   // hosts, e.g. "www.google.com". An empty host set produces an error.
   //
   // If an ongoing fetch exists, it will be cancelled and a new one started,
   // without triggering an additional callback (i.e. not noticeable by
   // subscriber of SetCallback()).
   //
   // Fetches snippets only if the daily quota not exceeded, unless
-  // |force_request| is set to true. Use force only for user-initiated fetches.
+  // |interactive_request| is set to true (use only for user-initiated fetches).
   void FetchSnippetsFromHosts(const std::set<std::string>& hosts,
                               const std::string& language_code,
                               int count,
-                              bool force_request);
+                              bool interactive_request);
 
   // Debug string representing the status/result of the last fetch attempt.
   const std::string& last_status() const { return last_status_; }
 
   // Returns the last JSON fetched from the server.
   const std::string& last_json() const {
     return last_fetch_json_;
   }
 
   // Returns the personalization setting of the fetcher.
@@ skipping 116 matching lines @@
   // Request throttler for limiting requests.
   RequestThrottler request_throttler_;
 
   base::WeakPtrFactory<NTPSnippetsFetcher> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsFetcher);
 };
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_FETCHER_H_