Make --force-fieldtrials not activate them in the browser process.

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"
 
 #if defined(TOOLKIT_GTK)
 #include <gtk/gtk.h>
 #endif
 
@@ skipping 592 matching lines @@
       new base::FieldTrialList(
           metrics->CreateEntropyProvider(metrics_reporting_enabled).release()));
 
   const CommandLine* command_line = CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableBenchmarking))
     base::FieldTrial::EnableBenchmarking();
 
   // Ensure any field trials specified on the command line are initialized.
   // Also stop the metrics service so that we don't pollute UMA.
   if (command_line->HasSwitch(switches::kForceFieldTrials)) {
-    std::string persistent = command_line->GetSwitchValueASCII(
-        switches::kForceFieldTrials);
-    bool ret = base::FieldTrialList::CreateTrialsFromString(persistent);
-    CHECK(ret) << "Invalid --" << switches::kForceFieldTrials <<
-                  " list specified.";
+    // 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(
+        command_line->GetSwitchValueASCII(switches::kForceFieldTrials),
+        base::FieldTrialList::DONT_ACTIVATE_TRIALS);
+    CHECK(result) << "Invalid --" << switches::kForceFieldTrials
+                  << " list specified.";
   }
 
   chrome_variations::VariationsService* variations_service =
       browser_process_->variations_service();
   if (variations_service)
     variations_service->CreateTrialsFromSeed();
 
   // This must be called after the local state is initialized.
   browser_field_trials_.SetupFieldTrials(local_state_);
 
@@ skipping 1143 matching lines @@
     if (base::win::GetVersion() <= base::win::VERSION_XP)
       uma_name += "_XP";
 
     uma_name += "_PreRead_";
     uma_name += pre_read_percentage;
     AddPreReadHistogramTime(uma_name.c_str(), time);
   }
 #endif
 #endif
 }