AudioWorkletGlobalScope is missing performance.now() (but has Date.now())

[juj]

Calling performance.now() is failing in Audio Worklets. However the inferior Date.now() does exist there.

It would be great to get performance.now() there as well, since most audio applications are likely about calculating audio synthesis timing, so will be looking at precise wallclock times, rather than imprecise Date calculations.

[hoch]

We're aware of the problem. The spec change will be presumably simple, but the impl might take a while.

Closing this as a duplicate of: #2413.