Fix layout regression in Site Details page (introduced by https://codereview.chromium.org/165255300…

chrome/browser/resources/settings/site_settings/site_details.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.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.html">
 <link rel="import" href="chrome://md-settings/site_settings/site_details_permission.html">
 <link rel="import" href="chrome://md-settings/site_settings/website_usage_private_api.html">
 
 <dom-module id="site-details">
   <link rel="import" type="css"
       href="chrome://md-settings/settings_shared.css">
   <link rel="import" type="css" href="site_details.css">
   <template>
-    <div class="settings-box">
+    <div class="settings-box block">
       <div class="origin">[[origin]]</div>
       <h2 i18n-content="siteSettingsUsage" id="usage"
           hidden$="[[!storedData_]]"></h2>
       <paper-item id="storage" hidden$="[[!storedData_]]">
         <div class="flex">[[storedData_]]</div>
         <paper-icon-button icon="delete"
             on-tap="onClearStorage_"
             i18n-values="alt:siteSettingsDelete"></paper-icon-button>
       </paper-item>
       <h2 i18n-content="siteSettingsPermissions"></h2>
@@ skipping 25 matching lines @@
           on-tap="onClearAndReset_"
           raised i18n-content="siteSettingsClearAndReset"
           class="reset-button"></paper-button>
     </div>
     <website-usage-private-api id="usageApi"
         website-data-usage="{{storedData_}}">
     </website-usage-private-api>
   </template>
   <script src="site_details.js"></script>
 </dom-module>