Remove support for the keygen tag

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

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.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-icon-button/paper-icon-button.html">
 <link rel="import" href="/route.html">
 <link rel="import" href="/settings_shared_css.html">
 <link rel="import" href="/site_settings/constants.html">
 <link rel="import" href="/site_settings/site_details_permission.html">
 <link rel="import" href="/site_settings/site_settings_behavior.html">
@@ skipping 79 matching lines @@
       </site-details-permission>
       <site-details-permission category="{{ContentSettingsTypes.POPUPS}}"
           icon="cr:open-in-new" id="popups" label="$i18n{siteSettingsPopups}"
           site="[[site]]">
       </site-details-permission>
       <site-details-permission
           category="{{ContentSettingsTypes.BACKGROUND_SYNC}}"
           icon="settings:sync" id="backgroundSync"
           label="$i18n{siteSettingsBackgroundSync}" site="[[site]]">
       </site-details-permission>
-      <site-details-permission category="{{ContentSettingsTypes.KEYGEN}}"
-          icon="settings:code" id="keygen"label="$i18n{siteSettingsKeygen}"
-          site="[[site]]">
-      </site-details-permission>
       <site-details-permission
           category="{{ContentSettingsTypes.AUTOMATIC_DOWNLOADS}}"
           icon="cr:file-download" id="automaticDownloads"
           label="$i18n{siteSettingsAutomaticDownloads}" site="[[site]]">
       </site-details-permission>
       <site-details-permission
           category="{{ContentSettingsTypes.UNSANDBOXED_PLUGINS}}"
           icon="cr:extension" id="unsandboxedPlugins"
           label="$i18n{siteSettingsUnsandboxedPlugins}" site="[[site]]">
       </site-details-permission>
 
       <div on-tap="onClearAndReset_" raised class="list-item list-button">
         $i18n{siteSettingsClearAndReset}
       </div>
     </div>
     <website-usage-private-api id="usageApi"
         website-data-usage="{{storedData_}}"
         website-storage-type="{{storageType_}}">
     </website-usage-private-api>
   </template>
   <script src="site_details.js"></script>
 </dom-module>