Revert "[EventTiming] Round instead of ceil the |duration|"

This reverts commit 9ac1e68e80f46289d00e6a1858740b89e34eb01e.

Reason for revert: This has make at least one of the timing tests flaky; tests probably need to be updated to account for the possible change in rounding direction.

Several bots started failing at roughly the same time, pointing to this CL as potential culprit.

Flakiness dashboad:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=external%2Fwpt%2Fevent-timing%2Fevent-timing-observethenonload.html&testType=webkit_layout_tests

Sample failure:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-xenial-rel/8797
https://test-results.appspot.com/data/layout_results/linux-xenial-rel/8797/webkit_layout_tests/layout-test-results/results.html

Original change's description:
> [EventTiming] Round instead of ceil the |duration|
> 
> The purpose of this change is to expose entries whose |duration| is >=
> 100ms.
> 
> Bug: 823744
> Change-Id: Ibb089009ba287769b1365a938cc7564278a86c35
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1594818
> Reviewed-by: Timothy Dresser <tdresser@chromium.org>
> Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#656797}

TBR=tdresser@chromium.org,npm@chromium.org

Change-Id: I1a048dcbb0fc62f3915195fb0f97158705db2d12
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 823744
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1596177
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#656839}
2 files changed