I'm migrating this from an inline issue:

Note: The timestamp values may be zero if the physical device reset timestamp counter, please ignore it and the following values.

Issue: Write normative text about timestamp value resets.

I do not know what needs to be written here. More detail from #614 which I assume is about the same thing:

Compute the difference of the two timestamp queries. The time delta may be negative due to the timestamp counter may be reset after a long time on some platforms. We can suggest users to skip the invalid time delta if it’s negative.

Regardless since this is defined in the V1 spec (even though implementations may ship without it, as Chrome does), marking as V1.