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

chrome/common/search/ntp_logging_events.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_COMMON_SEARCH_NTP_LOGGING_EVENTS_H_
 #define CHROME_COMMON_SEARCH_NTP_LOGGING_EVENTS_H_
 
 // The different types of events that are logged from the NTP. This enum is used
 // to transfer information from the NTP javascript to the renderer and is not
 // used as a UMA enum histogram's logged value.
 // Note: Keep in sync with browser/resources/local_ntp/most_visited_util.js
 // and browser/resources/local_ntp/most_visited_single.js
 enum NTPLoggingEventType {
   // The suggestion is coming from the server.
   NTP_SERVER_SIDE_SUGGESTION = 0,
 
   // The suggestion is coming from the client.
   NTP_CLIENT_SIDE_SUGGESTION = 1,
 
   // Indicates a tile was rendered, no matter if it's a thumbnail, a gray tile
   // or an external tile.
   NTP_TILE = 2,
 
   // The tile uses a local thumbnail image.
-  NTP_THUMBNAIL_TILE = 3,
+  // Deleted: NTP_THUMBNAIL_TILE = 3,
 
   // Used when no thumbnail is specified and a gray tile with the domain is used
   // as the main tile.
-  NTP_GRAY_TILE = 4,
+  // Deleted: NTP_GRAY_TILE = 4,
 
   // The visuals of that tile are handled externally by the page itself.
-  NTP_EXTERNAL_TILE = 5,
+  // Deleted: NTP_EXTERNAL_TILE = 5,
 
   // There was an error in loading both the thumbnail image and the fallback
   // (if it was provided), resulting in a grey tile.
-  NTP_THUMBNAIL_ERROR = 6,
+  // Deleted: NTP_THUMBNAIL_ERROR = 6,
 
   // Used a gray tile with the domain as the fallback for a failed thumbnail.
-  NTP_GRAY_TILE_FALLBACK = 7,
+  // Deleted: NTP_GRAY_TILE_FALLBACK = 7,
 
   // The visuals of that tile's fallback are handled externally.
-  NTP_EXTERNAL_TILE_FALLBACK = 8,
+  // Deleted: NTP_EXTERNAL_TILE_FALLBACK = 8,
 
   // Deleted: NTP_MOUSEOVER = 9
 
   // A NTP Tile has finished loading (successfully or failing).
   NTP_TILE_LOADED = 10,
 
   NTP_EVENT_TYPE_LAST = NTP_TILE_LOADED
 };
 
 // The source of an NTP tile.
 // Note: Keep in sync with browser/resources/local_ntp/most_visited_util.js and
 // browser/resources/local_ntp/most_visited_single.js.
 // TODO(treib): Merge this into MostVisitedSource from components/ntp_tiles.
 enum class NTPLoggingTileSource {
   CLIENT = 0,
   SERVER = 1,
   LAST = SERVER
 };
 
 #endif  // CHROME_COMMON_SEARCH_NTP_LOGGING_EVENTS_H_