[Research] zone + microtask

[vicb]

The first implementation of zone + microtask (see #82) works as follow:

• We use a monkey patch of Promise (es6-promise) so that we know when a microtask is scheduled,
• At the end of a macrotask, we execute pending microtasks (there is a check at then end of run())

That means than zone.js also acts as a scheduler for microtasks.

An other option would be to let JavaScript schedule microtasks. The JS implementation would become more similar to Dart zones.

• asap is a GH project that has several ways (to support most browsers) to enqueue microtasks.
• The fastest way to enqueue a microtask seems to be by using a resolved Promise, see Consider using Promise.prototype.then kriskowal/asap#54, http://blog.millermedeiros.com/promise-nexttick/, http://jsperf.com/test002/8

[vicb]

fixed in the last version of the linked PR (82)