Add the "options_ui" extension manifest field.

extensions/extensions_strings.grd

 <?xml version="1.0" encoding="utf-8"?>
 
 <!--
   Strings for the extensions module. Used mostly for low-level error messages.
   Where possible new strings should be kept in Chrome and the extensions module
   should return an error code, message flag, etc.
 -->
 
 <grit latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
@@ skipping 172 matching lines @@
       </message>
       <message name="IDS_EXTENSION_LOAD_BACKGROUND_PAGE_FAILED" desc="">
         Could not load background page '<ph name="BACKGROUND_PAGE">$1<ex>page.html</ex></ph>'.
       </message>
       <message name="IDS_EXTENSION_LOAD_ICON_FAILED" desc="">
         Could not load extension icon '<ph name="ICON">$1<ex>icon.png</ex></ph>'.
       </message>
       <message name="IDS_EXTENSION_LOAD_LAUNCHER_PAGE_FAILED" desc="">
         Could not load launcher page '<ph name="PAGE">$1<ex>index.html</ex></ph>'.
       </message>
+      <message name="IDS_EXTENSION_LOAD_OPTIONS_PAGE_FAILED" desc="">
+        Could not load options page '<ph name="OPTIONS_PAGE">$1<ex>page.html</ex></ph>'.
+      </message>
       <message name="IDS_EXTENSION_LOCALES_NO_DEFAULT_LOCALE_SPECIFIED" desc="">
         Localization used, but default_locale wasn't specified in the manifest.
       </message>
       <message name="IDS_EXTENSION_MANIFEST_UNREADABLE" desc="">
         Manifest file is missing or unreadable.
       </message>
       <message name="IDS_EXTENSION_MANIFEST_INVALID" desc="">
         Manifest file is invalid.
       </message>
 
@@ skipping 139 matching lines @@
       </message>
       <message name="IDS_EXTENSION_WARNING_RELOAD_TOO_FREQUENT" desc="Warning message which indates that an extension got stuck in a reload loop.">
         This extension reloaded itself too frequently.
       </message>
       <message name="IDS_EXTENSION_PROMPT_WARNING_U2F_DEVICES" desc="Warning message which indicates that an extension has access to Universal 2nd Factor devices.">
         Access your Universal 2nd Factor devices
       </message>
     </messages>
   </release>
 </grit>