Replace deprecated iron-flex-layout/classes with iron-flex-layout-class in MD Settings

chrome/browser/resources/settings/privacy_page/privacy_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
-<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/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="/clear_browsing_data_dialog/clear_browsing_data_dialog.html">
 <link rel="import" href="/controls/settings_checkbox.html">
 <link rel="import" href="/route.html">
 <link rel="import" href="/settings_page/settings_animated_pages.html">
 <link rel="import" href="/settings_page/settings_subpage.html">
 <link rel="import" href="/settings_shared_css.html">
 <link rel="import" href="/site_settings/all_sites.html">
 <link rel="import" href="/site_settings/constants.html">
@@ skipping 12 matching lines @@
 <dom-module id="settings-privacy-page">
   <template>
     <style include="settings-shared"></style>
     <template is="dom-if" if="[[showClearBrowsingDataDialog_]]" restamp>
       <settings-clear-browsing-data-dialog prefs="{{prefs}}"
           on-close="onDialogClosed_">
       </settings-clear-browsing-data-dialog>
     </template>
     <settings-animated-pages id="pages" section="privacy">
       <neon-animatable id="main">
-        <div class="settings-box block first">
+        <div class="settings-box single-column first">
           <p class="privacy-explanation">
             $i18nRaw{improveBrowsingExperience}
           </p>
           <settings-checkbox
               pref="{{prefs.alternate_error_pages.enabled}}"
               label="$i18n{linkDoctorPref}">
           </settings-checkbox>
           <settings-checkbox
               pref="{{prefs.search.suggest_enabled}}"
               label="$i18n{searchSuggestPref}"
@@ skipping 220 matching lines @@
       <template is="dom-if" name="site-details">
         <settings-subpage no-associated-control
             page-title="[[selectedSite.originForDisplay]]">
           <site-details site="[[selectedSite]]"></site-details>
         </settings-subpage>
       </template>
     </settings-animated-pages>
   </template>
   <script src="privacy_page.js"></script>
 </dom-module>