How would we manage customers who might be using the existing bindings?

I think this would probably need to be an alternate set of entrypoints in addition to the current ones. Over time we can deprecate the callback-style API if the new one proves to work better.

Tagging with canary milestone. 

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

We have a promises prototype in the works, but I don't think we'll be touching the C++ bindings for this.