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

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index d8608c9aca69b5f95a749f87c222f169251249ac..dc6939f2bf2a9fdb9461c163a98ec815384e7744 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -483,6 +483,24 @@ void LaunchDevToolsHandlerIfNeeded(const CommandLine& command_line) {
   }
 }
 
+// Returns true if the field trial described by |trial_name| is allowed to be
+// forced via --force-fieldtrials.
+bool IsForceableFieldTrial(const std::string& trial_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* const kUnforceableFieldTrials[] = {
+    "SettingsEnforcement",
+  };
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(KUnforceableFieldTrials); ++i) {
+    if (trial_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 {
@@ -518,6 +536,7 @@ void InitializeAllPrefHashStores() {
     chrome_prefs::InitializePrefHashStoreIfRequired(profile_path);
   }
 }
+
 }  // namespace
 
 namespace chrome_browser {
@@ -606,7 +625,8 @@ void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
     // 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));

[sky, 2014/02/12 18:17:30]

Is there a reason you need the function and can't pass in a vector? Seems more
straightforward.

[gab, 2014/02/12 23:38:37]

Nope, used a set instead; much easier, not sure why I didn't do that from the
get go... thanks for the suggestion!

     CHECK(result) << "Invalid --" << switches::kForceFieldTrials
                   << " list specified.";
   }