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

chrome/browser/resources/options/managed_user_set_passphrase.html

Index: chrome/browser/resources/options/managed_user_set_passphrase.html
diff --git a/chrome/browser/resources/options/managed_user_set_passphrase.html b/chrome/browser/resources/options/managed_user_set_passphrase.html
new file mode 100644
index 0000000000000000000000000000000000000000..f8a842dfe693a4d6585a0964f771d9a92174c3e0
--- /dev/null
+++ b/chrome/browser/resources/options/managed_user_set_passphrase.html
@@ -0,0 +1,24 @@
+<div id="managed-user-set-passphrase-overlay" class="page" hidden>
+  <div class="close-button"></div>
+  <h1 i18n-content="setPassphraseTitle"></h1>
+  <div class="content-area">
+    <div>
+      <span i18n-content="setPassphraseInstructions"></span>
+    </div>
+    <div class="managed-user-passphrase-container">
+      <input id="passphrase" type="password" align="center"
+          i18n-values=".placeholder:enterPassphrase" required>
+    </div>
+    <div class="managed-user-passphrase-container">
+      <input id="passphrase-confirm" class="equal_passphrases" type="password"
+          align="center" i18n-values=".placeholder:confirmPassphrase" required>
+    </div>
+    <div id="passphrase-mismatch" hidden>
+      <span i18n-content="passphraseMismatch"></span>
+    </div>
+    <div>
+      <button id="save-passphrase" i18n-content="savePassphrase" disabled>
+      </button>
+    </div>
+  </div>
+</div>