[Icon cacher] Add metrics for downloading favicons for NTP Tiles

components/ntp_tiles/icon_cacher_impl.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_TILES_ICON_CACHER_IMPL_H_
 #define COMPONENTS_NTP_TILES_ICON_CACHER_IMPL_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 65 matching lines @@
   void SaveAndNotifyDefaultIconForSite(
       const PopularSites::Site& site,
       const base::Closure& preliminary_icon_available,
       const gfx::Image& image);
   void SaveIconForSite(const PopularSites::Site& site, const gfx::Image& image);
 
   void OnGetLargeIconOrFallbackStyleFinished(
       const GURL& page_url,
       const favicon_base::LargeIconResult& result);
 
+  void OnMostLikelyFaviconDownloaded(const GURL& request_url, bool success);
+
   bool StartRequest(const GURL& request_url,
                     const base::Closure& icon_available);
   void FinishRequestAndNotifyIconAvailable(const GURL& request_url,
                                            bool newly_available);
 
   base::CancelableTaskTracker tracker_;
   favicon::FaviconService* const favicon_service_;
   favicon::LargeIconService* const large_icon_service_;
   std::unique_ptr<image_fetcher::ImageFetcher> const image_fetcher_;
   std::map<GURL, std::vector<base::Closure>> in_flight_requests_;
 
   base::WeakPtrFactory<IconCacherImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IconCacherImpl);
 };
 
 }  // namespace ntp_tiles
 
 #endif  // COMPONENTS_NTP_TILES_ICON_CACHER_IMPL_H_