[MD settings] using h2 for sub-headers consistently.

chrome/browser/resources/settings/search_engines_page/omnibox_extension_entry.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/icon.html">
 <link rel="import" href="/search_engines_page/search_engines_browser_proxy.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-dropdown/iron-dropdown.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-omnibox-extension-entry">
   <link rel="import" type="css" href="/search_engines_page/search_engine_entry.css">
   <template>
     <style include="settings-shared">
       .name-column {
         flex: 3;
       }
 
       .keyword-column {
         flex: 7;
       }
     </style>
-    <div id="container" class="list-item">
+    <div class="list-item">
       <div class="name-column">
         <span class="favicon-image"
             style="background-image: [[getIconSet_(engine.iconURL)]]"></span>
         <span class="name">[[engine.displayName]]</span>
       </div>
       <div class="keyword-column">[[engine.keyword]]</div>
       <paper-icon-button icon="cr:more-vert" toggles tabindex$="[[tabindex]]"
           active="{{editMenuOpened}}">
       </paper-icon-button>
       <iron-dropdown opened="{{editMenuOpened}}" horizontal-align="right"
           vertical-align="auto">
         <div class="dropdown-content">
           <button class="dropdown-item" role="option" on-tap="onManageTap_"
               id="manage">
             $i18n{searchEnginesManageExtension}
           </button>
           <button class="dropdown-item" role="option" on-tap="onDisableTap_"
               id="disable">
             $i18n{disable}
           </button>
         <div>
       </iron-dropdown>
     </div>
   </template>
   <script src="omnibox_extension_entry.js"></script>
 </dom-module>