external.js

$(document).ready(function() {
    function pageY(elem) {
        return elem.offsetParent ? (elem.offsetTop + pageY(elem.offsetParent)) : elem.offsetTop;
    }

    var buffer = 0; //scroll bar buffer

    function resizeIframe() {
        var height = document.documentElement.clientHeight;
        height -= pageY(document.getElementById('ifm')) + buffer;
        height = (height < 0) ? 0 : height;
        document.getElementById('ifm').style.height = height + 'px';
    }

    document.getElementById('ifm').onload = resizeIframe;
    window.onresize = resizeIframe;
});

frame.html

<div id="content-wrapper">
			<div id="content" class="app-external" role="main">
				<iframe id="ifm" src="https://mydraft.cc/"></iframe>
			</div>
		</div>