gentoo-overlay/mate-extra/mate-screensaver/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
    <herd>mate</herd>
	<use>
		<flag name="consolekit">Enable support for 
			<pkg>sys-auth/consolkekit</pkg></flag>
	</use>
    <upstream>
        <remote-id type="github">mate-desktop/mate-screensaver</remote-id>
    </upstream>
</pkgmetadata>