MD Settings: add a bunch of dialog (X) aria-labels

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

 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../icons.html">
 <link rel="import" href="lock_screen_constants.html">
 <link rel="import" href="pin_keyboard.html">
 <link rel="import" href="../settings_shared_css.html">
 
@@ skipping 15 matching lines @@
 
       .error > iron-icon {
         --iron-icon-fill-color: var(--paper-red-500);
       }
 
       .align-center {
         justify-content: center;
       }
     </style>
 
-    <dialog is="cr-dialog" id="dialog" on-close="close">
+    <dialog is="cr-dialog" id="dialog" on-close="close"
+        close-text="$i18n{close}">
       <div class="title">[[getTitleMessage_(isConfirmStep_)]]</div>
       <div class="body">
         <!-- Warning/error; only shown if title is hidden. Id is needed for
              tests. -->
         <div id="problemDiv" class$="[[problemClass_]] settings-box first"
              hidden$="[[!hasProblem_(problemMessage_)]]">
           <iron-icon icon="settings:warning"></iron-icon>
           <span class="middle">[[problemMessage_]]</span>
         </div>
 
@@ skipping 13 matching lines @@
                         disabled$="[[!enableSubmit_]]">
             <span>[[getContinueMessage_(isConfirmStep_)]]</span>
           </paper-button>
         </div>
       </div>
     </dialog>
   </template>
 
   <script src="setup_pin_dialog.js"></script>
 </dom-module>