Bug 1509859 [wpt PR 14234] - Align resource timing buffer full processing to spec...

Bug 1509859 [wpt PR 14234] - Align resource timing buffer full processing to spec PR 168 (reland), a=testonly

Automatic update from web-platform-tests
Align resource timing buffer full processing to spec PR 168 (reland)

This change implements the processing model from PR 168[1], when
it comes to setResourceTimingBufferSize(), clearResourceTimings()
and the firing of the resourcetimingbufferfull event.

This is a reland of
https://chromium-review.googlesource.com/c/chromium/src/+/1345269
(but with nicer tests).

[1] https://github.com/w3c/resource-timing/pull/168

Change-Id: I10431bfda7f79b484c7ee5c608bb8a360d905339
Bug: 908181, 908414
Reviewed-on: https://chromium-review.googlesource.com/c/1350950
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Yoav Weiss <yoavweiss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611174}

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wpt-commits: cccb52680a601f4de432124092c808e91fad8a15
wpt-pr: 14234