MD Settings: Restore focus after exiting Content settings sub-subpages.

chrome/browser/resources/settings/site_settings_page/site_settings_page.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-icon-button/paper-icon-button-light.html">
 <link rel="import" href="../icons.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="../site_settings/constants.html">
 <link rel="import" href="../site_settings/site_settings_behavior.html">
 <link rel="import" href="../site_settings/site_settings_prefs_browser_proxy.html">
 
 <dom-module id="settings-site-settings-page">
   <template>
     <style include="settings-shared">
       .settings-box iron-icon + .middle {
         -webkit-padding-start: 20px;
       }
     </style>
     <template is="dom-if" if="[[enableSiteSettings_]]">
       <div class="settings-box first" category$="[[ALL_SITES]]"
           data-route="SITE_SETTINGS_ALL" on-tap="onTapNavigate_" actionable>
         <iron-icon icon="settings:list"></iron-icon>
         <div class="middle">$i18n{siteSettingsCategoryAllSites}</div>
         <button class="subpage-arrow" is="paper-icon-button-light"
             aria-label="$i18n{siteSettingsCategoryAllSites}"></button>
       </div>
       <div class="settings-box line-only">
       </div>
     </template>
-    <div class="settings-box two-line first"
+    <div id="cookies" class="settings-box two-line first"
         category$="[[ContentSettingsTypes.COOKIES]]"
         data-route="SITE_SETTINGS_COOKIES" on-tap="onTapNavigate_" actionable>
       <iron-icon icon="settings:cookie"></iron-icon>
       <div class="middle">
         $i18n{siteSettingsCookies}
         <div class="secondary" id="cookiesSecondary">
           [[defaultSettingLabel_(
               default_.cookies,
               '$i18nPolymer{siteSettingsCookiesAllowed}',
               '$i18nPolymer{siteSettingsBlocked}',
               '$i18nPolymer{deleteDataPostSession}')]]
         </div>
       </div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{siteSettingsCookies}"
           aria-describedby="cookiesSecondary"></button>
     </div>
-    <div class="settings-box two-line"
+    <div id="location" class="settings-box two-line"
         category$="[[ContentSettingsTypes.GEOLOCATION]]"
         data-route="SITE_SETTINGS_LOCATION" on-tap="onTapNavigate_" actionable>
       <iron-icon icon="settings:location-on"></iron-icon>
       <div class="middle">
         $i18n{siteSettingsLocation}
         <div class="secondary" id="locationSecondary">
           [[defaultSettingLabel_(
               default_.location,
               '$i18nPolymer{siteSettingsAskBeforeAccessing}',
               '$i18nPolymer{siteSettingsBlocked}')]]
         </div>
       </div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{siteSettingsLocation}"
           aria-describedby="locationSecondary"></button>
     </div>
-    <div class="settings-box two-line"
+    <div id="camera" class="settings-box two-line"
         category$="[[ContentSettingsTypes.CAMERA]]"
         data-route="SITE_SETTINGS_CAMERA"
         on-tap="onTapNavigate_" actionable>
       <iron-icon icon="settings:videocam"></iron-icon>
       <div class="middle">
         $i18n{siteSettingsCamera}
         <div class="secondary" id="cameraSecondary">
           [[defaultSettingLabel_(
               default_.mediaStreamCamera,
               '$i18nPolymer{siteSettingsAskBeforeAccessing}',
               '$i18nPolymer{siteSettingsBlocked}')]]
         </div>
       </div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{siteSettingsCamera}"
           aria-describedby="cameraSecondary"></button>
     </div>
-    <div class="settings-box two-line" category$="[[ContentSettingsTypes.MIC]]"
+    <div id="microphone" class="settings-box two-line"
+        category$="[[ContentSettingsTypes.MIC]]"
         data-route="SITE_SETTINGS_MICROPHONE" on-tap="onTapNavigate_"
         actionable>
       <iron-icon icon="settings:mic"></iron-icon>
       <div class="middle">
         $i18n{siteSettingsMic}
         <div class="secondary" id="micSecondary">
           [[defaultSettingLabel_(
               default_.mediaStreamMic,
               '$i18nPolymer{siteSettingsAskBeforeAccessing}',
               '$i18nPolymer{siteSettingsBlocked}')]]
@@ skipping 229 matching lines @@
     <div class="settings-box" data-route="SITE_SETTINGS_PROTECTED_CONTENT"
         on-tap="onTapNavigate_" actionable>
       <iron-icon icon="settings:security"></iron-icon>
       <div class="middle">$i18n{siteSettingsProtectedContent}</div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{siteSettingsProtectedContent}"></button>
     </div>
   </template>
   <script src="site_settings_page.js"></script>
 </dom-module>