src/third_party/web_platform_tests/conformance-checkers/html/attributes/data/not-xml-serializable-novalid.html - cobalt - Git at Google

 <!doctype html>
 <meta charset=utf-8>
 <title>starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no uppercase ASCII letters</title>
 <p data-z:foo=""><!-- not serializable as XML -->
	<!doctype html>
	<meta charset=utf-8>
	<title>starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no uppercase ASCII letters</title>
	<p data-z:foo=""><!-- not serializable as XML -->