Add a lock to the managed user settings page and require authentication for unlocking.

chrome/browser/managed_mode/managed_mode.cc

Index: chrome/browser/managed_mode/managed_mode.cc
diff --git a/chrome/browser/managed_mode/managed_mode.cc b/chrome/browser/managed_mode/managed_mode.cc
index f1acb3bb8d0ffcd1605fd03699af7a25c2bd6c2c..caa0e51888e6c8d4cad8e5986a01905935672435 100644
--- a/chrome/browser/managed_mode/managed_mode.cc
+++ b/chrome/browser/managed_mode/managed_mode.cc
@@ -91,6 +91,9 @@ void ManagedMode::RegisterUserPrefs(PrefServiceSyncable* prefs) {
   prefs->RegisterIntegerPref(prefs::kDefaultManagedModeFilteringBehavior,
                              2,
                              PrefServiceSyncable::UNSYNCABLE_PREF);
+  prefs->RegisterStringPref(prefs::kManagedModeLocalPassphrase,
+                            "default",

[Bernhard Bauer, 2013/01/07 14:20:22]

I think an empty string would be better as a default value (a human-readable
string would make me think it's the clear text passphrase, but it's the hash,
right?).

[Pam (message me for reviews), 2013/01/07 14:51:49]

I think we should make this empty as a default, and if the passphrase is empty,
then we don't show a dialog asking for one. That lets custodians choose not to
lock the settings if they prefer.

The first part of that can be done here; the second part (skipping the dialogs
when there's no passphrase) can be done in a later change.

+                            PrefServiceSyncable::UNSYNCABLE_PREF);
 }
 
 // static