registry.xml

<?xml version="1.0"?>
<registry>

  <records prefix="plone.resources/mytheme-resources"
            interface="Products.CMFPlone.interfaces.IResourceRegistry">
    <value key="js">++theme++mytheme/js/mytheme-custom.js</value>
    <value key="css">
      <element>++theme++mytheme/less/mytheme-main.less</element>
    </value>
  </records>

  <records prefix="plone.bundles/mytheme-bundle"
            interface="Products.CMFPlone.interfaces.IBundleRegistry">
    <value key="resources">
      <element>mytheme-resources</element>
    </value>
    <value key="depends">plone</value>
    <value key="enabled">True</value>
    <value key="compile">True</value>
    <value key="jscompilation">++theme++mytheme/mytheme-bundle-compiled.js</value>
    <value key="csscompilation">++theme++mytheme/mytheme-bundle-compiled.css</value>
    <value key="last_compilation">2015-10-31 00:00:00</value>
  </records>

</registry>