Consider Worker Fallbacks

[runspired]

When the Worker API is not present, fall back to the main-thread as efficiently as possible.

We could simply include the worker script onto the main thread and async the calls via a custom backburner queue after afterRender.

We could implement the worker within an iFrame.

We could provide app/workers/<worker-name>/fallback.js ability that has a main-thread optimized version of the workers' tasks.

This task is low priority as workers are widely available IE10+. The primary reason to consider this is for when an API feature is unexpectedly not available within a WebWorker.