Add a mechanism to force parameters of a group to a specific value.

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 <set>
 #include <string>
 #include <vector>
 
@@ skipping 619 matching lines @@
   field_trial_list_.reset(
       new base::FieldTrialList(metrics->CreateEntropyProvider().release()));
 
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableBenchmarking) ||
       command_line->HasSwitch(cc::switches::kEnableGpuBenchmarking)) {
     base::FieldTrial::EnableBenchmarking();
   }
 
+  if (command_line->HasSwitch(switches::kForceFieldTrialParams)) {
+    variations::AssociateParamsFromString(
+      command_line->GetSwitchValueASCII(switches::kForceFieldTrialParams));
+  }
+
   // Ensure any field trials specified on the command line are initialized.
   if (command_line->HasSwitch(switches::kForceFieldTrials)) {
     std::set<std::string> unforceable_field_trials;
 #if defined(OFFICIAL_BUILD)
     unforceable_field_trials.insert("SettingsEnforcement");
 #endif  // defined(OFFICIAL_BUILD)
 
     // Create field trials without activating them, so that this behaves in a
     // consistent manner with field trials created from the server.
     bool result = base::FieldTrialList::CreateTrialsFromString(
@@ skipping 1120 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);
 }