LayoutTests/http/tests/security/resources/cross-frame-iframe-for-get-test.html

<iframe name="testiframe" src="data:text/html,<p>test iframe</p>"></iframe>
<img name="testimage" src="data:image/jpg,">
<script>
window.existingCustomProperty = 1; 
window.Object.prototype.prototypeCustomProperty = 1;
</script>