Desktop NTP: Add a UMA metric NewTabPage.TilesReceivedTime

chrome/browser/ui/webui/ntp/ntp_user_data_logger.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 CHROME_BROWSER_UI_WEBUI_NTP_NTP_USER_DATA_LOGGER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_NTP_USER_DATA_LOGGER_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 37 matching lines @@
                                 ntp_tiles::NTPTileSource tile_source);
 
  protected:
   explicit NTPUserDataLogger(content::WebContents* contents);
 
  private:
   friend class content::WebContentsUserData<NTPUserDataLogger>;
 
   FRIEND_TEST_ALL_PREFIXES(NTPUserDataLoggerTest, TestLogMostVisitedImpression);
   FRIEND_TEST_ALL_PREFIXES(NTPUserDataLoggerTest, TestNumberOfTiles);
+  FRIEND_TEST_ALL_PREFIXES(NTPUserDataLoggerTest, TestLoadTime);
 
   // Number of Most Visited elements on the NTP for logging purposes.
   static const int kNumMostVisited = 8;
 
   // content::WebContentsObserver override
   void NavigationEntryCommitted(
       const content::LoadCommittedDetails& load_details) override;
 
   // Implementation of NavigationEntryCommitted; separate for test.
   void NavigatedFromURLToURL(const GURL& from, const GURL& to);
@@ skipping 10 matching lines @@
   // If something happens that causes the NTP to pull tiles from different
   // sources, such as signing in (switching from client to server tiles), then
   // only the impressions for the first source will be logged, leaving the
   // number of impressions for a source slightly out-of-sync with navigations.
   std::bitset<kNumMostVisited> impression_was_logged_;
 
   // Stores the tile source for each impression. Entries are only valid if the
   // corresponding entry in |impression_was_logged_| is true.
   std::vector<ntp_tiles::NTPTileSource> impression_tile_source_;
 
+  // The time we received the NTP_ALL_TILES_RECEIVED event.
+  base::TimeDelta tiles_received_time_;
+
   // Whether we have already emitted NTP stats for this web contents.
   bool has_emitted_;
 
   // Are stats being logged during Chrome startup?
   bool during_startup_;
 
   // The URL of this New Tab Page - varies based on NTP version.
   GURL ntp_url_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPUserDataLogger);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_NTP_USER_DATA_LOGGER_H_