[whatwg] [WebWorkers] About the delegation example

[ben turner]

I think it's important to note that there is no guarantee that each
worker is tied to an actual OS-level thread. Firefox, for instance,
will schedule workers on a limited number of OS threads to prevent
resource swamping. Other implementations (Chromium only?) create new
processes to run worker code. The only guarantee is that code executed
in a worker will not block the main thread.

-Ben