Popular sites on the NTP: Extend UMA histograms that track clicks and impressions

chrome/browser/android/most_visited_sites.h

Index: chrome/browser/android/most_visited_sites.h
diff --git a/chrome/browser/android/most_visited_sites.h b/chrome/browser/android/most_visited_sites.h
index e378e8501bb8bbb5f964eead693eff0ab95fe80d..6f4abbeeb1bab9f38970eba6c5ff0375b3514b49 100644
--- a/chrome/browser/android/most_visited_sites.h
+++ b/chrome/browser/android/most_visited_sites.h
@@ -79,9 +79,9 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
 
   // Adds the suggestions from |popular_sites_| into |titles| and |urls|. This
   // might reorder |titles| and |urls| to retain the absolute positions of the
-  // popular suggestions.
+  // popular suggestions. Also updates |tile_sources_| accordingly.
   void AddPopularSites(std::vector<base::string16>* titles,
-                       std::vector<std::string>* urls) const;
+                       std::vector<std::string>* urls);
 
   // Workhorse for AddPopularSites above. Implemented as a separate static
   // method for ease of testing.
@@ -89,6 +89,7 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
       int num_sites,
       std::vector<base::string16>* titles,
       std::vector<std::string>* urls,
+      std::vector<std::string>* tile_sources,
       const std::vector<base::string16>& popular_titles,
       const std::vector<std::string>& popular_urls);
 
@@ -112,8 +113,11 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
       const GURL& url,
       const SkBitmap* bitmap);
 
-  // Records specific UMA histogram metrics.
-  void RecordUMAMetrics();
+  // Records thumbnail-related UMA histogram metrics.
+  void RecordThumbnailUMAMetrics();
+
+  // Records UMA histogram metrics related to the number of impressions.
+  void RecordImpressionUMAMetrics();
 
   // history::TopSitesObserver implementation.
   void TopSitesLoaded(history::TopSites* top_sites) override;
@@ -142,8 +146,9 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
   // In this case a gray tile is used as the main tile.
   int num_empty_thumbs_;
 
-  // Copy of the server suggestions (if enabled). Used for logging.
-  suggestions::SuggestionsProfile server_suggestions_;
+  // Identifier for where each tile came from (client, server, popular). Used
+  // for logging.
+  std::vector<std::string> tile_sources_;
 
   ScopedObserver<history::TopSites, history::TopSitesObserver> scoped_observer_;