Use postMessage to tell the parent window the size of the current window height - for parent window implementation see https://gist.github.com/ianchadwick/a4e277d641bf739063c9

cross-domain-iframe-height.js

<script>
    /**
     * For parent window implementation details
     * @see https://gist.github.com/ianchadwick/a4e277d641bf739063c9
     */
    (function (speed) {
        if (parent === window) {
            // no parent frame!
            return;
        }

        // make sure the scroll bars are hidden on the html element
        document.documentElement.style.overflow = 'hidden';

        var height = 0;

        var watchForChanges = function () {
            height = window.document.body.getBoundingClientRect().height;
            parent.postMessage('iframe-height|' + window.location + '|' + height, '*');
            setTimeout(watchForChanges, speed);
        };
        watchForChanges();
    }(200));
</script>