Switch to MutationObserver

[briancavalier]

This drops setImmediate and MessageChannel support, relying primarily on process.nextTick for all Node versions, and adding MutationObserver support as the "fast" browser scheduler. Vert.x support is unchanged, and everything falls back to setTimeout when no fast option is detected.

Definitely looking for feedback.

Fix #197

[unscriptable]

So this works multiple times? The 'x' attribute doesn't have to change its value?

[briancavalier]

Apparently, yeah. I've run some tests in Chrome and it works. I plan to let Travis run the full gamut of tests on all platforms when this lands in dev as well. Also, this is how RSVP implements it

[briancavalier]

Ok, I slimmed the MO branch down by removing the unload workaround.

[briancavalier]

A couple nice benefits of this approach:

1. It cuts the time-to-first-handler in half on Chrome 29 (haven't tested on other recent chromes)
2. It reduces that time by about 25% on FF 24, and stabilizes it. We were falling back to setTimeout on FF, which is notoriously inconsistent.

One obvious downside:

1. It forces IE10 to fall back to setTimeout. Only way to deal with this for now would be to introduce a postMessage or other additional hack.

[unscriptable]

Combination of IE10 mobile + setTimeout concerns me.

[briancavalier]

Merging after more discussion with @unscriptable, and in light of the fact that postMessage suffers the same problem. I'm ok with IE10 getting setTimeout. If we discover that either onreadystatechange or requestAnimationFrame is somehow a better alternative, we can consider introducing one of them.

[briancavalier]

All green on Travis and Saucelabs tests. At least we know we haven't broken the world :)

[stefanpenner]

👍