MD Settings: hide signin-related UI when signin is disabled (e.g. by policy)

chrome/browser/resources/settings/people_page/people_page.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/icon.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="/controls/settings_checkbox.html">
@@ skipping 77 matching lines @@
               [[profileName_]]
             </span>
 </if>
 <if expr="chromeos">
             <span id="profile-name">
               [[profileName_]]
             </span>
 </if>
           </div>
 <if expr="not chromeos">
-          <template is="dom-if" if="[[!syncStatus.signedIn]]">
+          <template is="dom-if" if="[[showSignin_(syncStatus)]]">
             <span class="secondary-action">
               <paper-button class="primary-button" on-tap="onSigninTap_"
                   disabled="[[syncStatus.setupInProgress]]">
                 $i18n{syncSignin}
               </paper-button>
             </span>
           </template>
           <template is="dom-if" if="[[syncStatus.signedIn]]">
             <span class="secondary-action">
               <paper-button id="disconnectButton" class="secondary-button"
                   on-tap="onDisconnectTap_"
                   disabled="[[syncStatus.setupInProgress]]">
                 $i18n{syncDisconnect}
               </paper-button>
             </span>
           </template>
 </if>
         </div>
-        <div class="settings-box two-line" hidden="[[syncStatus.signedIn]]">
+        <div class="settings-box two-line"
+            hidden="[[!showSignin_(syncStatus)]]">
           $i18n{syncOverview}
         </div>
 
 <if expr="not chromeos">
         <template is="dom-if" if="[[syncStatus.domain]]">
           <div class="settings-box">
             <div class="icon-container">
               <iron-icon icon="cr:domain"></iron-icon>
             </div>
             <div class="middle"
@@ skipping 191 matching lines @@
 
 <if expr="chromeos">
     <template is="dom-if" if="[[easyUnlockEnabled_]]">
       <easy-unlock-turn-off-dialog id="easyUnlockTurnOffDialog">
       </easy-unlock-turn-off-dialog>
     </template>
 </if>
   </template>
   <script src="people_page.js"></script>
 </dom-module>