Cleanup the Win overlapped reads vs. non-blocking reads by removing the overlapped read code path

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 <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 710 matching lines @@
                                 abandoned_page ? 1 : 0, 2);
     } else {
       DCHECK(scheme_type == URLPattern::SCHEME_HTTP);
       PLT_HISTOGRAM("PLT.StartToFinish.NoProxy.http",
                     start_to_finish_all_loads);
       UMA_HISTOGRAM_ENUMERATION("PLT.Abandoned.NoProxy.http",
                                 abandoned_page ? 1 : 0, 2);
     }
   }
 
-  // Histograms to determine if disabling overlapped TCP reads
-  // has an impact on PLT.
-  static const bool use_overlapped_read_histogram =
-      base::FieldTrialList::TrialExists("OverlappedReadImpact");
-  if (use_overlapped_read_histogram) {
-    UMA_HISTOGRAM_ENUMERATION(
-        base::FieldTrial::MakeName("PLT.Abandoned", "OverlappedReadImpact"),
-        abandoned_page ? 1 : 0, 2);
-    UMA_HISTOGRAM_ENUMERATION(
-        base::FieldTrial::MakeName("PLT.LoadType", "OverlappedReadImpact"),
-        load_type, DocumentState::kLoadTypeMax);
-    switch (load_type) {
-      case DocumentState::NORMAL_LOAD:
-        PLT_HISTOGRAM(base::FieldTrial::MakeName(
-            "PLT.BeginToFinish_NormalLoad", "OverlappedReadImpact"),
-            begin_to_finish_all_loads);
-        break;
-      case DocumentState::LINK_LOAD_NORMAL:
-        PLT_HISTOGRAM(base::FieldTrial::MakeName(
-            "PLT.BeginToFinish_LinkLoadNormal", "OverlappedReadImpact"),
-            begin_to_finish_all_loads);
-        break;
-      case DocumentState::LINK_LOAD_RELOAD:
-        PLT_HISTOGRAM(base::FieldTrial::MakeName(
-            "PLT.BeginToFinish_LinkLoadReload", "OverlappedReadImpact"),
-            begin_to_finish_all_loads);
-        break;
-      case DocumentState::LINK_LOAD_CACHE_STALE_OK:
-        PLT_HISTOGRAM(base::FieldTrial::MakeName(
-            "PLT.BeginToFinish_LinkLoadStaleOk", "OverlappedReadImpact"),
-            begin_to_finish_all_loads);
-        break;
-      default:
-        break;
-    }
-  }
-
   // Site isolation metrics.
   UMA_HISTOGRAM_COUNTS("SiteIsolation.PageLoadsWithCrossSiteFrameAccess",
                        cross_origin_access_count_);
   UMA_HISTOGRAM_COUNTS("SiteIsolation.PageLoadsWithSameSiteFrameAccess",
                        same_origin_access_count_);
 
   // Log the PLT to the info log.
   LogPageLoadTime(document_state, frame->dataSource());
 
   // Since there are currently no guarantees that renderer histograms will be
@@ skipping 34 matching lines @@
 
   DCHECK(document_state);
   DCHECK(ds);
   GURL url(ds->request().url());
   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();
 }