Remove old prefetcher histogram code in render_frame_impl

chrome/renderer/page_load_histograms.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/renderer/page_load_histograms.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
@@ skipping 476 matching lines @@
     case DocumentState::LINK_LOAD_CACHE_ONLY:
       PLT_HISTOGRAM("PLT.BeginToFinishDoc_LinkLoadCacheOnly",
            begin_to_finish_doc);
       PLT_HISTOGRAM("PLT.BeginToFinish_LinkLoadCacheOnly",
                     begin_to_finish_all_loads);
       break;
     default:
       break;
   }
 
-  if (document_state->was_prefetcher()) {
-    PLT_HISTOGRAM("PLT.BeginToFinishDoc_ContentPrefetcher",
-                  begin_to_finish_doc);
-    PLT_HISTOGRAM("PLT.BeginToFinish_ContentPrefetcher",
-                  begin_to_finish_all_loads);
-  }
-  if (document_state->was_referred_by_prefetcher()) {
-    PLT_HISTOGRAM("PLT.BeginToFinishDoc_ContentPrefetcherReferrer",
-                  begin_to_finish_doc);
-    PLT_HISTOGRAM("PLT.BeginToFinish_ContentPrefetcherReferrer",
-                  begin_to_finish_all_loads);
-  }
-
   const bool use_webrequest_histogram = WasWebRequestUsedBySomeExtensions();
   if (use_webrequest_histogram) {
     switch (load_type) {
       case DocumentState::NORMAL_LOAD:
         PLT_HISTOGRAM(
             "PLT.BeginToFinish_NormalLoad_ExtensionWebRequest",
             begin_to_finish_all_loads);
         break;
       case DocumentState::LINK_LOAD_NORMAL:
         PLT_HISTOGRAM(
@@ skipping 111 matching lines @@
   Time start = document_state->start_load_time();
   Time finish = document_state->finish_load_time();
   // TODO(mbelshe): should we log more stats?
   VLOG(1) << "PLT: " << (finish - start).InMilliseconds() << "ms "
           << url.spec();
 }
 
 void PageLoadHistograms::OnDestruct() {
   delete this;
 }