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

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

 <link rel="import" href="chrome://resources/cr_elements/cr_profile_avatar_selector/cr_profile_avatar_selector.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/paper-input/paper-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="manage_profile_browser_proxy.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <dom-module id="settings-manage-profile">
   <template>
     <style include="settings-shared">
       #selector {
         margin: 16px 20px;
       }
     </style>
     <div class="settings-box first">
       <paper-input id="name" value="[[profileName]]" pattern=".*\S.*"
           auto-validate required on-change="onProfileNameChanged_"
           disabled="[[isProfileNameDisabled_(syncStatus)]]">
       </paper-input>
     </div>
     <template is="dom-if" if="[[isProfileShortcutSettingVisible_]]">
       <div class="settings-box first">
-        <div class="flex">$i18n{showShortcutLabel}</div>
+        <div id="showShortcutLabel" class="flex">$i18n{showShortcutLabel}</div>
         <paper-toggle-button id="hasShortcutToggle"
             checked="{{hasProfileShortcut_}}"
-            on-change="onHasProfileShortcutChange_">
+            on-change="onHasProfileShortcutChange_"
+            aria-labelledby="showShortcutLabel">
         </paper-toggle-button>
       </div>
     </template>
     <cr-profile-avatar-selector id="selector" avatars="[[availableIcons]]"
         selected-avatar-url="{{profileIconUrl}}"
         on-iron-activate="onIconActivate_" ignore-modified-key-events>
     </cr-profile-avatar-selector>
   </template>
   <script src="manage_profile.js"></script>
 </dom-module>