I agree with most of the concerns raised above, but on another matter:
I thought of other clocks which, if added, would be best added via the stdlib: ProcessClock, TaskClock and possibly ThreadClock. These would be (mathematically) monotonic clocks which only and regularly tick while, respectfully, the current (or a particular other?) process, task or thread is running.
A possible use for these would be benchmarking: if a user stops and then resumes the test runner in the middle of a benchmark, I would consider it reasonable for the time while stopped to not be included in the benchmark's running time, which none of the currently proposed clocks would permit.