Handle the PasswordManagerAllowShowPasswords preference in the options webui.

chrome/browser/resources/options/personal_options.html

 <div id="personal-page" class="page hidden">
   <h1 i18n-content="personalPage"></h1>
 
 <if expr="pp_ifdef('chromeos')">
   <section>
     <h3 i18n-content="account"></h3>
     <div>
       <table class="option-control-table">
         <tr>
           <td>
@@ skipping 55 matching lines @@
       <div class="radio">
         <label>
           <input id="passwords-neversave" type="radio" name="passwords_radio"
               value="false" pref="profile.password_manager_enabled"
               metric="Options_PasswordManager">
           <span i18n-content="passwordsNeverSave"></span>
         </label>
       </div>
       <div><button id="manage-passwords"
           i18n-content="manage_passwords"></button></div>
+      <!-- This makes the managed-banner appear when the "pref" is
+      configured by the IT administrator. -->
+      <input name="password_allow_show_hidden" type="text"
+          pref="profile.password_manager_allow_show_passwords" hidden>
     </div>
   </section>
   <section>
     <h3 i18n-content="autofill"></h3>
     <div>
       <div class="checkbox">
         <label>
           <input id="autofillEnabled" pref="autofill.enabled"
               metric="Options_FormAutofill" type="checkbox">
           <span i18n-content="autofillEnabled"></span>
@@ skipping 53 matching lines @@
       </div>
       <div id="themes-gallery-div">
         <a id="themes-gallery" i18n-content="themesGallery"
             i18n-values="href:themesGalleryURL" target="_blank"></a>
       </div>
     </div>
   </section>
 </if>
 
 </div>