Remove a bunch of broken/unused/non-useful NTP UMA histograms

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 <string>
-
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "chrome/common/search/ntp_logging_events.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
 class WebContents;
 }
 
 // Helper class for logging data from the NTP. Attached to each NTP instance.
@@ skipping 10 matching lines @@
   // incremented. |time| is the delta time in ms from navigation start until
   // this event happened.
   void LogEvent(NTPLoggingEventType event, base::TimeDelta time);
 
   // Logs an impression on one of the NTP tiles by a given source.
   void LogMostVisitedImpression(int position, NTPLoggingTileSource tile_source);
 
   // Logs a navigation on one of the NTP tiles by a given source.
   void LogMostVisitedNavigation(int position, NTPLoggingTileSource tile_source);
 
-  // content::WebContentsObserver override
-  void NavigationEntryCommitted(
-      const content::LoadCommittedDetails& load_details) override;
-
   // Called when the tab is closed. Logs statistics.
   void TabDeactivated();
 
   // Called when the set of most visited sites changes. Flushes statistics.
   void MostVisitedItemsChanged();
 
  protected:
   explicit NTPUserDataLogger(content::WebContents* contents);
 
  private:
   friend class content::WebContentsUserData<NTPUserDataLogger>;
 
   FRIEND_TEST_ALL_PREFIXES(SearchTabHelperTest,
                            OnMostVisitedItemsChangedFromServer);
   FRIEND_TEST_ALL_PREFIXES(SearchTabHelperTest,
                            OnMostVisitedItemsChangedFromClient);
   FRIEND_TEST_ALL_PREFIXES(NTPUserDataLoggerTest,
                            TestLogging);
 
+  // content::WebContentsObserver override
+  void NavigationEntryCommitted(
+      const content::LoadCommittedDetails& load_details) override;
+
   // To clarify at the call site whether we are calling EmitNtpStatistics() for
   // a good reason (CLOSED, NAVIGATED_AWAY) or a questionable one (MV_CHANGED,
   // INTERNAL_FLUSH).
   // TODO(sfiera): remove MV_CHANGED, INTERNAL_FLUSH.
   enum class EmitReason { CLOSED, NAVIGATED_AWAY, MV_CHANGED, INTERNAL_FLUSH };
 
   // Logs a number of statistics regarding the NTP. Called when an NTP tab is
   // about to be deactivated (be it by switching tabs, losing focus or closing
   // the tab/shutting down Chrome), or when the user navigates to a URL.
   void EmitNtpStatistics(EmitReason reason);
 
   // True if at least one iframe came from a server-side suggestion.
   bool has_server_side_suggestions_;
 
   // True if at least one iframe came from a client-side suggestion.
   bool has_client_side_suggestions_;
 
   // Total number of tiles rendered, no matter if it's a thumbnail, a gray tile
   // or an external tile.
   size_t number_of_tiles_;
 
-  // Total number of tiles using a local thumbnail image for this NTP session.
-  size_t number_of_thumbnail_tiles_;
-
-  // Total number of tiles for which no thumbnail is specified and a gray tile
-  // with the domain is used as the main tile.
-  size_t number_of_gray_tiles_;
-
-  // Total number of tiles for which the visual appearance is handled externally
-  // by the page itself.
-  size_t number_of_external_tiles_;
-
-  // Total number of errors that occurred when trying to load thumbnail images
-  // for this NTP session. When these errors occur a grey tile is shown instead
-  // of a thumbnail image.
-  size_t number_of_thumbnail_errors_;
-
-  // The number of times a gray tile with the domain was used as the fallback
-  // for a failed thumbnail.
-  size_t number_of_gray_tile_fallbacks_;
-
-  // The number of times an external tile, for which the visual appearance is
-  // handled by the page itself, was the fallback for a failed thumbnail.
-  size_t number_of_external_tile_fallbacks_;
-
   // Time from navigation start it took to load the NTP in milliseconds.
   base::TimeDelta load_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_