function trimTrailingBr(rootNode) {
		var brNode1, brNode2;

		function isBr(node) {
			return node && node.name === 'br';
		}

		brNode1 = rootNode.lastChild;
		if (isBr(brNode1)) {
			brNode2 = brNode1.prev;

			if (isBr(brNode2)) {
				brNode1.remove();
				brNode2.remove();
			}
		}
	}
IE 11 has a fantastic bug where it will produce two trailing BR elements to iframe bodies when
the iframe is hidden by display: none on a parent container. The DOM is actually out of sync
with innerHTML in this case. It's like IE adds shadow DOM BR elements that appears on innerHTML
but not as the lastChild of the body. So this fix simply removes the last two
BR elements at the end of the document.

Example of what happens: <body>text</body> becomes <body>text<br><br></body>