Adds iframe code for #9239.

test/data/support/bodyBackground.html

+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en" dir="ltr" id="html">
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+	<style>
+		body {
+			background: #000000;
+		}
+	</style>
+</head>
+<body>
+	<div>
+		<script src="../../../src/core.js"></script>
+		<script src="../../../src/deferred.js"></script>
+		<script src="../../../src/support.js"></script>
+		<script src="../../../src/data.js"></script>
+		<script src="../../../src/queue.js"></script>
+		<script src="../../../src/attributes.js"></script>
+		<script src="../../../src/event.js"></script>
+		<script src="../../../src/sizzle/sizzle.js"></script>
+		<script src="../../../src/sizzle-jquery.js"></script>
+		<script src="../../../src/traversing.js"></script>
+		<script src="../../../src/manipulation.js"></script>
+		<script src="../../../src/css.js"></script>
+		<script src="../../../src/ajax.js"></script>
+		<script src="../../../src/ajax/jsonp.js"></script>
+		<script src="../../../src/ajax/script.js"></script>
+		<script src="../../../src/ajax/xhr.js"></script>
+		<script src="../../../src/effects.js"></script>
+		<script src="../../../src/offset.js"></script>
+		<script src="../../../src/dimensions.js"></script>
+	</div>
+	<script>
+		window.top.supportCallback( jQuery( "body" ).css( "backgroundColor" ), jQuery.support );
+	</script>
+</body>
+</html>