Tests failing on IE11

[sorvell]

The Update Ref test fails. Fwiw, I did notice that if I put a setTimeout, 0 around the failing assert, the test passes.

[jmesserly]

It looks like setTimeout 0 is firing before (native) MutationObservers in IE11... which should be impossible...

[sorvell]

Ug, I was afraid it might be something like that. Ideally if we can make a small repro we can post an IE issue and then workaround the bug in the test.

[jmesserly]

ah. was chatting with arv & he confirmed that IE doesn't have microtasks. Sadness!

I'll put in a workaround for now. Fortunately, I don't think this will show up in typical Polymer apps, since Shadow DOM Polyfill includes a MutationObserver polyfill, which respects the order better. (That also explains why we didn't see this failure elsewhere.) Of course, something to keep in mind if we optimize SD polyfill to use native M.O. when possible.

[sorvell]

That's sad but sounds reasonable. Thanks @jmesserly.

[jmesserly]

https://codereview.appspot.com/125250044/