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

chrome/browser/resources/managed_user_passphrase_dialog.css

Index: chrome/browser/resources/managed_user_passphrase_dialog.css
diff --git a/chrome/browser/resources/managed_user_passphrase_dialog.css b/chrome/browser/resources/managed_user_passphrase_dialog.css
new file mode 100644
index 0000000000000000000000000000000000000000..ac538b69315e9ec3ed2258991813e3908f43d95b
--- /dev/null
+++ b/chrome/browser/resources/managed_user_passphrase_dialog.css
@@ -0,0 +1,30 @@
+#family-control-passphrase-page {

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

WHAT IS THIS FAMILY CONTROL YOU SPEAK OF

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

You need the copyright/license header here.

/* 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. */

+  min-width: 350px;
+}
+
+#instruct {

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

Don't use abbreviations in identifiers (you probably want to say
"instructions"?).

+  padding: 5px 15px;

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

I think you could group these selectors.

+}
+
+#entry {
+  padding: 5px 15px;
+}
+
+#ref {
+  padding: 1px 15px;
+}
+
+#unlock {
+  float: right;
+}
+
+#buttons {
+  padding: 15px 15px;
+}
+
+#incorrect_passphrase_warning {

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

DOM IDs use hyphens to separate words.

+  color: red;
+  font-weight: bold;
+  padding: 5px 15px;
+  visibility: hidden;
+}