MD Settings: Add missing cr-hidden-style in settings_subpage_search.html.

chrome/browser/resources/settings/settings_page/settings_subpage_search.html

 <link rel="import" href="chrome://resources/cr_elements/cr_search_field/cr_search_field_behavior.html">
+<link rel="import" href="chrome://resources/cr_elements/hidden_style_css.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/polymer/v1_0/iron-icon/iron-icon.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-input/paper-input-container.html">
 
 <dom-module id="settings-subpage-search">
   <template>
-    <style>
+    <style include="cr-hidden-style">
       :host {
         --subpage-search-underline: {
           margin-bottom: -2px;
           margin-top: -2px;
         }
       }
 
       :host {
         --paper-input-container-underline: var(--subpage-search-underline);
         --paper-input-container-underline-focus:
@@ skipping 50 matching lines @@
           on-input="onSearchTermInput" aria-labelledby="prompt" incremental
           autofocus$="[[autofocus]]" placeholder="[[label]]">
       <paper-icon-button suffix icon="cr:cancel" id="clearSearch"
           on-tap="onTapClear_" title="[[clearLabel]]"
           hidden$="[[!hasSearchText]]">
       </paper-icon-button>
     </paper-input-container>
   </template>
   <script src="settings_subpage_search.js"></script>
 </dom-module>