[ASDisplayNode] Expose already-implemented asynchronous measurement method.

[appleguy]

A method exists in ASDisplayNode that's actually not called right now: _enqueueAsyncSizingWithSentinel.

This should be used (or removed), and one use case would be ASViewController if a developer indicated they wanted the ASVC to begin preparing its content before it's onscreen so that layout doesn't block. This ASVC functionality wouldn't be that difficult to implement, but requires thinking carefully about the API; there are at least three types of preloading that would make sense to trigger, including network-only fetches, layout measurement, and doing both of those + full rendering pass.

[appleguy]

The community is planning an exciting long term road map for the project and getting organized around how to deliver these feature requests. We are moving to a new issue tracker with more sophisticated planning capabilities (check out www.realArtists.com and their new product: Ship!).

If you are interested in helping contribute to this component or any other, don’t hesitate to send me an email at AsyncDisplayKit@gmail.com. If you would like to contribute for a few weeks, I can also add you to our Ship bug tracker so that you can see what everyone is working on and actively coordinate with us.

As always, keep filing issues and submitting pull requests here on Github and we will only move things to the new tracker if they require long term coordination.