DOMHighResTimeStamp property giving platform time for DOM events

Hello,

This discussion originally started back in March (
http://lists.w3.org/Archives/Public/public-web-perf/2012Mar/0034.html) and
as suggested was moved to the www-dom mailing list where after some
discussion and cases where the timestamp would be useful (
http://lists.w3.org/Archives/Public/www-dom/2012AprJun/0092.html) it was
suggested that we move it back to the web performance spec (
http://lists.w3.org/Archives/Public/www-dom/2012OctDec/0028.html) since we
use this spec as a baseline to be able to compare these monotonic
timestamps.

I've put a patch up for review with a proposal implementation of this
feature (https://bugs.webkit.org/show_bug.cgi?id=94987) in WebKit which
uses the PlatformEvent timestamp to accurately provide the monotonic system
time responsible for the creation of the DOM event as a time since document
load consistent with Performance.now(). I'd love to see this added to the
spec so that we can track the latency of events in ECMAScript since arrival
to the system kernel.

Since the spec for Event.timeStamp requires a 1970 epoch based time it is
unsuitable for measuring the latency of events at a high level for the same
reasons Performance.now() exists.

Thanks for the help in moving this discussion forward,
Rob