Add one-time randomization support for FieldTrial, and the ability to

net/url_request/url_request_http_job.cc

 // Copyright (c) 2011 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 "net/url_request/url_request_http_job.h"
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
@@ skipping 1079 matching lines @@
   if (request_creation_time_.is_null()) {
     NOTREACHED()
         << "The same transaction shouldn't start twice without new timing.";
     return;
   }
 
   base::TimeDelta to_start = base::Time::Now() - request_creation_time_;
   request_creation_time_ = base::Time();
 
   static const bool use_prefetch_histogram =
-      base::FieldTrialList::Find("Prefetch") &&
-      !base::FieldTrialList::Find("Prefetch")->group_name().empty();
+      base::FieldTrialList::TrialExists("Prefetch");
 
   UMA_HISTOGRAM_MEDIUM_TIMES("Net.HttpTimeToFirstByte", to_start);
   if (use_prefetch_histogram) {
     UMA_HISTOGRAM_MEDIUM_TIMES(
         base::FieldTrial::MakeName("Net.HttpTimeToFirstByte",
                                    "Prefetch"),
         to_start);
   }
 
   const bool is_prerender = !!(request_info_.load_flags & LOAD_PRERENDER);
@@ skipping 257 matching lines @@
 }
 
 bool URLRequestHttpJob::IsCompressibleContent() const {
   std::string mime_type;
   return GetMimeType(&mime_type) &&
       (IsSupportedJavascriptMimeType(mime_type.c_str()) ||
        IsSupportedNonImageMimeType(mime_type.c_str()));
 }
 
 }  // namespace net