[jerf]

If I'm reading this correctly, this is a library for use within a browser, in which case the answer is that this makes it easier to live within the constraints of the browser, which has arguably the strangest "multitasking" support anywhere, what with all the constraints it had to satisfy to be added in to an architecture already 15 years old at that point.

[astoilkov]

Yeah, that sums it up. The library tries to use the single thread the browser UI is running on and just not freeze it.