Extend the SequenceManagerPerf to support cross thread posting

Cross thread immediate task posting performance matters for the UI
thread and the Blink main thread.  This patch adds a perf test for this
case.

Also refactors things into classes which hopefully makes it a bit more
manageable.

Bug: 863341, 897751
Change-Id: I5cc1492fb1988582085af0c4ff04ac7e729a4fd7
Reviewed-on: https://chromium-review.googlesource.com/c/1307500
Reviewed-by: Alexander Timin <[email protected]>
Reviewed-by: Sami Kyöstilä <[email protected]>
Commit-Queue: Alex Clarke <[email protected]>
Cr-Commit-Position: refs/heads/master@{#604215}
1 file changed