Lock request queues are never initialized

[saschanaz]

https://wicg.github.io/web-locks/#algorithm-request-lock

2. Enqueue the following steps to the lock task queue:
   1. Let queueMap be origin’s lock request queue map.
   2. Let queue be queueMap[name].

But nothing actually set queueMap[name], so queue is always nonexistent.

[inexorabletash]

Good catch.

There are four instances of "Let queue be queueMap[name]" - we can either:

• add a preceding step: "If queueMap[name] does not exist, then set queueMap[name] to a new lock request queue." in all four cases; or
• add a new algorithm for "get the lock request queue from a lock request queue map" that populates and returns it.

@pwnall - Any preferences?

[pwnall]

I prefer the algorithm approach. And this happens to match the PR you have up. :+1: