Spec text isn't clear about time origins and monotonic clocks

[jyasskin]

In spec order:

• "The time origin is the time value from which time is measured" <- what is a time value?
• get time origin timestamp: "Let t1 be the DOMHighResTimeStamp representing the high resolution time at which the shared monotonic clock is zero." <- what is a high resolution time? The fact that it's a DOMHighResTimeStamp doesn't help, since those have 3 possible meanings: "measured relative from the time origin, shared monotonic clock, or a time value".
• "the high resolution time value at which time origin is zero." <- It doesn't make sense to talk about a time at which "the time value from which time is measured" is zero.
• Monotonic clock and shared monotonic clock aren't really defined.
• The sentences "monotonic clock" and "shared monotonic clock" appear in are COMEFROM requirements: in order to have an effect, they need to be placed inside the definitions of now() and timeOrigin, respectively.
• It's not clear what "not subject to ... system clock skew" would mean. If it's just that the monotonic clock's values aren't comparable across machines, we should probably say that directly.
• "whose reference point is the [ECMA-262] time definition" is the only use of "reference point" in this document or ECMA-262. What do we mean by it? If it's that the shared monotonic clock needs to measure time with its 0 at the epoch, and needs to jump at leap seconds, the latter conflicts with the idea of a monotonic clock.