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

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 465 matching lines @@
           chrome::HOST_DESKTOP_TYPE_NATIVE,
           "127.0.0.1",
           port,
           frontend_str);
     } else {
       DLOG(WARNING) << "Invalid http debugger port number " << port;
     }
   }
 }
 
+// Returns true if the field trial described by |name| is allowed to be forced
+// via --force-fieldtrials.
+bool IsForceableFieldTrial(const std::string& name) {
+#if defined(OFFICIAL_BUILD)
+  // A list of field trials which cannot be forced to a different value in the
+  // official build.
+  static const char* KUnforceableFieldTrials[] = {

[Alexei Svitkine (slow), 2014/02/11 22:44:02]

Nit: Lowercase k. Also, I don't think this needs to be static.

[gab, 2014/02/11 22:53:55]

Done.

Yes it needs to be static; it's a compound type (an array) and would otherwise
undergo a copy from .rodata.

See
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/pF7nAmUQ2uw/wrNhX...
for details.

+    "SettingsEnforcement",
+  };
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(KUnforceableFieldTrials); ++i) {
+    if (name == KUnforceableFieldTrials[i])
+      return false;
+  }
+#endif  // defined(OFFICIAL_BUILD)
+
+  return true;
+}
+
 // Heap allocated class that listens for first page load, kicks off stat
 // recording and then deletes itself.
 class LoadCompleteListener : public content::NotificationObserver {
  public:
   LoadCompleteListener() {
     registrar_.Add(this,
                    content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
                    content::NotificationService::AllSources());
   }
   virtual ~LoadCompleteListener() {}
@@ skipping 15 matching lines @@
 void InitializeAllPrefHashStores() {
   ProfileInfoCache& profile_info_cache =
       g_browser_process->profile_manager()->GetProfileInfoCache();
   size_t n_profiles = profile_info_cache.GetNumberOfProfiles();
   for (size_t i = 0; i < n_profiles; ++i) {
     base::FilePath profile_path =
         profile_info_cache.GetPathOfProfileAtIndex(i);
     chrome_prefs::InitializePrefHashStoreIfRequired(profile_path);
   }
 }
+
 }  // namespace
 
 namespace chrome_browser {
 
 // This error message is not localized because we failed to load the
 // localization data files.
 #if defined(OS_WIN)
 const char kMissingLocaleDataTitle[] = "Missing File Error";
 #endif
 
@@ skipping 68 matching lines @@
   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)) {
     // 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);
+        base::FieldTrialList::DONT_ACTIVATE_TRIALS,
+        base::Bind(&IsForceableFieldTrial));
     CHECK(result) << "Invalid --" << switches::kForceFieldTrials
                   << " list specified.";
   }
   if (command_line->HasSwitch(switches::kForceVariationIds)) {
     // Create default variation ids which will always be included in the
     // X-Client-Data request header.
     chrome_variations::VariationsHttpHeaderProvider* provider =
         chrome_variations::VariationsHttpHeaderProvider::GetInstance();
     bool result = provider->SetDefaultVariationIds(
         command_line->GetSwitchValueASCII(switches::kForceVariationIds));
@@ skipping 1077 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif
 #endif
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }