[Prerender] Get the prerender mode from Finch field trial.

chrome/browser/chrome_browser_main.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/browser/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <set>
@@ skipping 605 matching lines @@
 
 // BrowserMainParts ------------------------------------------------------------
 
 ChromeBrowserMainParts::ChromeBrowserMainParts(
     const content::MainFunctionParams& parameters)
     : parameters_(parameters),
       parsed_command_line_(parameters.command_line),
       result_code_(content::RESULT_CODE_NORMAL_EXIT),
       startup_watcher_(new StartupTimeBomb()),
       shutdown_watcher_(new ShutdownWatcherHelper()),
-      browser_field_trials_(parameters.command_line),
       sampling_profiler_(
           base::PlatformThread::CurrentId(),
           StackSamplingConfiguration::Get()->
               GetSamplingParamsForCurrentProcess(),
           metrics::CallStackProfileMetricsProvider::GetProfilerCallback(
               metrics::CallStackProfileParams(
                   metrics::CallStackProfileParams::BROWSER_PROCESS,
                   metrics::CallStackProfileParams::UI_THREAD,
                   metrics::CallStackProfileParams::PROCESS_STARTUP,
                   metrics::CallStackProfileParams::MAY_SHUFFLE))),
@@ skipping 1456 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }