GitLab

Reduce flakiness in layout test http/tests/misc/resource-timing-sizes-tags.html
by:
* Using the PerformanceObserver interface to reliably detect when a performance
  entry is available.
* Removing the invisible objects before completion to reduce the risk that it
  will be misdetected as a DOM test.

Other miscellaneous cleanups have been applied.

BUG=786235

Change-Id: Iaefbd5ee6adecad23ef39035091ba454523413f8
Reviewed-on: https://chromium-review.googlesource.com/1111893Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569959}