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Avoids racing to make up lost samples, and the bias resulting from that
behavior, in the case where the sample tasks didn't execute on the
expected schedule. This can happen during system suspend or in cases
of system-wide jank. The correct solution is to skip the samples and
continue sampling at the regular cadence, since the system was not
actively executing in the interim.

Expected impacts:

For the UMA case, reduced bias towards execution immediately following
resume. There will still be some bias towards the first 30 seconds of
execution after resume because the profile scheduling remains unaware
of suspend/resume cycles.

For the tracing case, aligns the sampling exactly to the specified
sampling interval on average. The sampling in the existing implementation
was actually occurring on average at the specified interval plus half
the timer tick interval.

Bug: 876063
Change-Id: I6c0894bc9909131a4632765c6a6acc4678763bdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2199918
Commit-Queue: Mike Wittman <wittman@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771192}