<iframe id=resizeThis style="width: 600px; height: 100px; border: 5px solid red;" src="data:text/html,<input type='input'><br>
1. Activate the input field to zoom in<br>
2. Rotate the device to landscape and back to portrait while zoomed in<br>
3. Double tap to zoom out<br>
iframe has different size now.
<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar<br>foobar"></iframe>
<script>
resizeThis.style.height = window.innerHeight - 50;

window.addEventListener('resize', function() {
  resizeThis.style.height = window.innerHeight - 50;
});
</script>