Unify iron-dropdown CSS

chrome/browser/resources/settings/languages_page/languages_page.html

 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.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-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_expand_button/cr_expand_button.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
@@ skipping 12 matching lines @@
 <if expr="chromeos">
 <link rel="import" href="manage_input_methods_page.html">
 </if>
 
 <dom-module id="settings-languages-page">
   <template>
     <style include="settings-shared">
       .list-button {
         @apply(--settings-actionable);
       }
-
-      .dropdown-content {
-        background: white;
-        box-shadow: 0 2px 6px grey;
-      }
-
-      paper-item:hover {
-        background-color: var(--settings-hover-color);
-      }
     </style>
     <settings-languages languages="{{languages}}"></settings-languages>
     <settings-animated-pages id="pages" current-route="{{currentRoute}}"
         section="languages">
       <neon-animatable id="main">
         <div class="settings-box first two-line">
           <div class="start">
             <div>$i18n{languagesListTitle}</div>
             <div class="secondary">
               [[getProspectiveUILanguageName_(
@@ skipping 165 matching lines @@
       <template is="dom-if" name="edit-dictionary">
         <settings-subpage page-title="$i18n{editDictionaryPageTitle}">
           <settings-edit-dictionary-page></settings-edit-dictionary-page>
         </settings-subpage>
       </template>
 </if>
     </settings-animated-pages>
   </template>
   <script src="languages_page.js"></script>
 </dom-module>