crossbrowser failure in test - Iframe onload not triggered on some platforms

[kumavis]

Note this should only be a problem for the tests, not the lib itself
https://ci.testling.com/npm-dom/iframe

iexplore/10.0
open  debug in browserling  close
TAP version 13
# it adds an iframe to the document by default
ok 1 no frames
ok 2 one frame
# it removes the iframe from the document
ok 3 no frames
ok 4 one frame
ok 5 no frames
# it renders the iframe contents as html, not plaintext
ok 6 no frames
ok 7 one frame

The iframe's load event seems to not be triggered on some platforms

[kumavis]

The contentDocument is replaced entirely when the blob is loaded, so adding events on it on iframe creation do not fire.

The correct event for IE may be readystatedidchange