Issue with IE11 and CSS loading

[JoseGoncalves]

I have found an issue in fallback when using it with IE11. If the CSS class used to test the correct loading of a given CSS file is declared with the same value than other class(es), in a comma separated list, it fails to be detected in IE11 (but works in IE10 and IE9). Please check this Plunkr that demonstrates that issue in a Kendo UI app.

[Blackbaud-ChristiSchneider]

I believe this commit has caused some issues with IE11.

Here is a plunkr which demonstrates a similar issue.

Because of the ActiveXObject line that was added specifically for IE11, fallback believes that my sky_css dependency has failed to load, even though it loaded properly with a 200 response according to the network tab. Because page_css depends on sky_css, fallback never attempts to load app.css and instead uses the specified shim. When I revert commit 5bf3cc9, the issue no longer occurs in IE11.