MD Settings: Style native <select> down arrow.

chrome/browser/resources/settings/search_page/search_page.html

 <link rel="import" href="chrome://resources/html/polymer.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="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="/md_select_css.html">
 <link rel="import" href="/route.html">
 <link rel="import" href="/search_engines_page/search_engines_page.html">
 <link rel="import" href="/search_engines_page/search_engines_browser_proxy.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">
 
 <dom-module id="settings-search-page">
   <template>
     <style include="settings-shared md-select"></style>
     <settings-animated-pages id="pages" section="search">
       <neon-animatable route-path="default">
         <div class="settings-box first">
           <p class="start">$i18n{searchExplanation}</p>
           <div>
-            <select on-change="onChange_">
+            <select class="md-select" on-change="onChange_">
               <template is="dom-repeat" items="[[searchEngines_]]">
                 <option selected$="[[item.default]]">[[item.name]]</option>
               </template>
             </select>
-            <span class="select-underline"></span>
+            <span class="md-select-underline"></span>
           </div>
         </div>
         <div id="subpage-trigger" class="settings-box two-line"
             on-tap="onManageSearchEnginesTap_" actionable>
           <div class="start">
             $i18n{searchEnginesManage}
             <div class="secondary">
               $i18n{searchEnginesManageDescription}
             </div>
           </div>
           <button class="icon-arrow-right" is="paper-icon-button-light">
           </button>
         </div>
       </neon-animatable>
       <template is="dom-if" route-path="/searchEngines">
         <settings-subpage
             associated-control="[[$$('#subpage-trigger')]]"
             page-title="$i18n{searchEnginesManage}">
           <settings-search-engines-page></settings-search-engines-page>
         </settings-subpage>
       </template>
     </settings-animated-pages>
   </template>
   <script src="search_page.js"></script>
 </dom-module>