MD-Settings: Adds an a11y label to most toggle buttons.

chrome/browser/resources/settings/languages_page/languages_page.html

 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/action_link_css.html">
 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.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-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
@@ skipping 192 matching lines @@
         <iron-collapse id="spellCheckCollapse" opened="[[spellCheckOpened_]]">
           <div class="list-frame vertical-list">
             <template is="dom-repeat" items="[[languages.enabled]]">
               <div class="list-item">
                 <div class="start" on-tap="onSpellCheckChange_"
                     actionable$="[[item.language.supportsSpellcheck]]">
                   [[item.language.displayName]]
                 </div>
                 <paper-toggle-button on-change="onSpellCheckChange_"
                     disabled="[[!item.language.supportsSpellcheck]]"
-                    checked="[[item.spellCheckEnabled]]">
+                    checked="[[item.spellCheckEnabled]]"
+                    aria-label$="[[item.language.displayName]]">

[dschuyler, 2017/02/22 23:43:33]

aria-label$= is used here, while aria-label= is used elsewhere in this CL.
Do they need to be different?

[Dan Beam, 2017/02/23 00:00:38]

yes

                 </paper-toggle-button>
               </div>
             </template>
             <div class="list-item">
               <a is="action-link" class="list-button"
                   on-tap="onEditDictionaryTap_">
                 $i18n{manageSpellCheck}
               </a>
             </div>
           </div>
@@ skipping 69 matching lines @@
 </if>
     </settings-animated-pages>
     <template is="dom-if" if="[[showAddLanguagesDialog_]]" restamp>
       <settings-add-languages-dialog languages="{{languages}}"
           language-helper="[[languageHelper]]">
       </settings-add-languages-dialog>
     </template>
   </template>
   <script src="languages_page.js"></script>
 </dom-module>