optimize debounce pattern in pf 3.0

[aFarkas]

See discussion here

[aFarkas]

@baloneysandwiches
Do you want to take this?

[albell]

Yes. I would prefer to localize all debouncing logic in a single function and not have timer stuff sprinkled all around, if possible. I would like to get rid of resizeThrottle if we can. Looking at:

https://github.com/scottjehl/picturefill/blob/afarkas-pf3-proposal/src/picturefill.js#L1324-L1327

is there a reason we need this? Is resize ever going to happen before setupRun?

[aFarkas]

This line is a micro optimization. If a developer calls the API while we wait for a debounced call, we abort the debounced call. Due to the fact that this won't happen so often... you are free to remove it.

[albell]

I took a quick stab at this but it's failing a handful of functional tests. I suspect this has to do with the async tests not playing well with the debounce timer. I hesitate to go build delays into the tests to make them pass. Can you take a look?

albell@2925378