Make some field trials unforceable via command-line in the official build.

content/renderer/renderer_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 "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/debug/debugger.h"
 #include "base/debug/stack_trace.h"
 #include "base/debug/trace_event.h"
 #include "base/i18n/rtl.h"
@@ skipping 175 matching lines @@
   // Initialize statistical testing infrastructure.  We set the entropy provider
   // to NULL to disallow the renderer process from creating its own one-time
   // randomized trials; they should be created in the browser process.
   base::FieldTrialList field_trial_list(NULL);
   // Ensure any field trials in browser are reflected into renderer.
   if (parsed_command_line.HasSwitch(switches::kForceFieldTrials)) {
     // Field trials are created in an "activated" state to ensure they get
     // reported in crash reports.
     bool result = base::FieldTrialList::CreateTrialsFromString(
         parsed_command_line.GetSwitchValueASCII(switches::kForceFieldTrials),
-        base::FieldTrialList::ACTIVATE_TRIALS);
+        base::FieldTrialList::ACTIVATE_TRIALS,
+        std::set<std::string>());
     DCHECK(result);
   }
 
 #if defined(ENABLE_PLUGINS)
   // Load pepper plugins before engaging the sandbox.
   PepperPluginRegistry::GetInstance();
 #endif
 #if defined(ENABLE_WEBRTC)
   // Initialize WebRTC before engaging the sandbox.
   // NOTE: On linux, this call could already have been made from
@@ skipping 41 matching lines @@
       base::MessageLoop::current()->Run();
       TRACE_EVENT_END_ETW("RendererMain.START_MSG_LOOP", 0, 0);
     }
   }
   platform.PlatformUninitialize();
   TRACE_EVENT_END_ETW("RendererMain", 0, "");
   return 0;
 }
 
 }  // namespace content