R1:98899c822eb9

Conpherence - kill race conditions around update

Summary:
Fixes T6713. The idea is to keep checking what's going on in the update paths that touch the DOM. If we're doing an update or should be doing a different update, then we bail early.

This is the type of code + testing that makes me dizzy after awhile, but I think it works...

Test Plan:
added a "forceStall" parameter to the column view controller, which when specified sleeps for seconds before returning. I then augmented the JS such that the "send…