src/core/support.js

define( [
	"../var/document",
	"../var/support"
], function( document, support ) {

"use strict";

if ( window.trustedTypes && window.trustedTypes.createPolicy ) {
	support.createHTMLDocument = ( function() {
		return true;
	} );
} else {

	// Support: Safari 8 only
	// In Safari 8 documents created via document.implementation.createHTMLDocument
	// collapse sibling forms: the second one becomes a child of the first one.
	// Because of that, this security measure has to be disabled in Safari 8.
	// https://bugs.webkit.org/show_bug.cgi?id=137337
	support.createHTMLDocument = ( function() {
		var body = document.implementation.createHTMLDocument( "" ).body;
		body.innerHTML = "<form></form><form></form>";
		return body.childNodes.length === 2;
	} )();
}

return support;
} );