Mark TimeTicks::UnixEpoch deprecated

Internal MacOS TimeTicks function is using mach_absolute_time[1] which
is suspended while system is asleep[3].
TimeTicks::UnixEpoch is returning a static value that is computed on the
first call.
This means that TimeTicks::UnixEpoch will not take into account system
suspension and any TimeTicks comparison after such suspension will be
offset by that amount (often hours or days).

IMHO, this function should be removed as the TimeTicks documentation
clearly states[2] that TimeTicks is for process duration and not to
track absolute time (base::Time instead).

[1]: https://developer.apple.com/documentation/kernel/1462446-mach_absolute_time
[2]: https://source.chromium.org/chromium/chromium/src/+/main:base/time/time.h;l=40
[3]: https://source.chromium.org/chromium/chromium/src/+/main:base/time/time.h;l=16

Bug: 349542284
Change-Id: Icc96a90612d9a50cf5f67e5c6c1610c87d3cfd07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5731604
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1336580}
NOKEYCHECK=True
GitOrigin-RevId: 1a6106ec2fc932237359fe1f54334a66bc4886f1
1 file changed