ChromeOS OOBE: fix focus flow in MD-OOBE.

chrome/browser/resources/chromeos/login/oobe_eula.html

 <!-- Copyright 2016 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. -->
 
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-iconset-svg/iron-iconset-svg.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 
 <iron-iconset-svg name="oobe-eula" size="24">
   <svg>
     <defs>
       <!-- The Google "G" icon (copied from md-settings). -->
       <g id="googleg">
         <path fill="#4285F4" d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92c-.26 1.37-1.04 2.53-2.21 3.31v2.77h3.57c2.08-1.92 3.28-4.74 3.28-8.09z"></path>
         <path fill="#34A853" d="M12 23c2.97 0 5.46-.98 7.28-2.66l-3.57-2.77c-.98.66-2.23 1.06-3.71 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84C3.99 20.53 7.7 23 12 23z"></path>
         <path fill="#FBBC05" d="M5.84 14.09c-.22-.66-.35-1.36-.35-2.09s.13-1.43.35-2.09V7.07H2.18C1.43 8.55 1 10.22 1 12s.43 3.45 1.18 4.93l2.85-2.22.81-.62z"></path>
         <path fill="#EA4335" d="M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.07l3.66 2.84c.87-2.6 3.3-4.53 6.16-4.53z"></path>
         <path fill="none" d="M1 1h22v22H1z"></path>
       </g>
     </defs>
   </svg>
 </iron-iconset-svg>
 
 <dom-module name="oobe-eula-md">
   <template>
     <link rel="stylesheet" href="oobe_eula.css">
     <link rel="stylesheet" href="oobe_dialog_parameters.css">
-    <oobe-dialog hidden="[[!eulaLoadingScreenShown]]"
+    <oobe-dialog id="eulaLoadingDialog" hidden="[[!eulaLoadingScreenShown]]"
+        role="dialog" aria-label="$i18n{termsOfServiceLoading}"
         has-buttons>
       <iron-icon icon="oobe-eula:googleg" class="oobe-icon"></iron-icon>
       <div class="header">
         <h1 class="title" i18n-content="termsOfServiceLoading"></h1>
       </div>
     </oobe-dialog>
-    <oobe-dialog hidden="[[!eulaScreenShown]]"
+    <oobe-dialog id="eulaDialog" hidden="[[eulaLoadingScreenShown]]"
+        role="dialog" aria-label="$i18n{oobeEulaSectionTitle}"
         has-buttons>
       <iron-icon icon="oobe-eula:googleg" class="oobe-icon"></iron-icon>
       <div class="header">
         <h1 class="title" i18n-content="oobeEulaSectionTitle"></h1>
       </div>
       <div class="footer flex layout vertical">
-        <iframe id="crosEulaFrame" class="flex" src="chrome://terms"
+        <iframe id="crosEulaFrame" src="chrome://terms"
+            role="document" class="flex focus-on-show"
+            aria-label="$i18n{oobeEulaIframeLabel}"
             on-load="onFrameLoad_">
         </iframe>
         <a id="installationSettings" href="#"
             on-tap="onInstallationSettingsClicked_"
             i18n-content="eulaSystemInstallationSettings">
         </a>
         <div id="logging">
           <paper-checkbox aria-labelledby="usage-stats-label" id="usageStats"
               checked="{{usageStatsChecked}}" on-change="onUsageChanged_">
             <label id="usage-stats-label" i18n-content="checkboxLogging">
@@ skipping 12 matching lines @@
         <oobe-text-button id="eula-accept-button" inverse on-tap="eulaAccepted_"
             disabled="[[acceptButtonDisabled]]">
           <div i18n-content="oobeEulaAcceptAndContinueButtonText"
               id="accept-button-text">
           </div>
         </oobe-text-button>
       </div>
     </oobe-dialog>
   </template>
 </dom-module>