Editorial: collapse "actively needed" and "protected" for workers

[domenic]

It turns out these concepts are identical, and it was just very hard to tell. Proof:

• "protected" implies "actively needed": immediate from their existing definitions.

• "actively needed" implies "protected": the key is that for an actively needed worker, "the worker's ports" is never empty, so step 3 will always return true. In particular, for dedicated workers, their implicit MessagePort can never be removed from "the worker's ports", since there is no exposed MessagePort object that could be transferred or close()ed or garbage collected. And shared workers are always protected.

Stated another way, despite the complicated definition of "protected", it is not possible to have a worker that is "actively needed" but not "protected". The extra clause about outstanding timers, database transactions, or network connections is redundant.

This is a follow-up to e9ccb97. The text prior to that revision also supports this conclusion.

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It would be good to get a check on this from worker experts like @yoshisatoyanagisawa, @asutherland, or @fergald. In particular I'm curious if there was an underlying implementation distinction here, which the spec was trying to make but failed to do so.

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/workers.html ( diff )

[domenic]

Actually I think this is wrong. The case of "actively needed" but not "protected" might be: a dedicated worker doing a bunch of computation, with no outstanding timers/database transactions/etc., whose corresponding Worker object got garbage collected.

Closing, and will open a different clarification PR to point that out.