CPU hot plugging

In its present form, this API assumes that CPU information (i.e., the CPU model and number of cores) does not change with time. This is not necessarily true, in the presence of CPU hot plugging, which amounts to adding or removing processing units, physically or virtually, while the computer system remains operational. Virtualization platforms typically offer this functionality, but an operating system may also arbitrarily decide to enable or disable CPU units, so that the reported number of logical cores changes.

If CPU information changes, it is probably expected that the value reported by navigator.cpuPerformance may also change.

Furthermore, if CPU hot plugging represents a significant use case, maybe it makes sense to add some observer to this API, similarly to what the Compute Pressure API does.

I am opening this here for discussion.
[This was first mentioned by Sangwhan Moon here.]

Start with the issue discussion and the linked Blink-dev thread about CPU hot plugging. Determine whether navigator.cpuPerformance should reflect changing CPU information and whether an observer is needed; the issue is done when the API behavior and any observer requirement are decided.