dillon1000/react

Convert CallbackQueue to a class (#7647)

It turns out that flow cannot type `this` with a function constructor + prototype overrides. Turning it to a class makes flow happy and has minimal impact on the output.

In open source, we already use the loose version of the class transform and internally we have one that's outputting even less code if you have `@preventMunge` in the header.

See discussion in https://www.facebook.com/groups/2003630259862046/permalink/2098480820376989/