Ignore fixed and sticky elements in JankTracker.

These were generating spurious janks on scroll, because the visual rect
moves.  (The old / new rects are mapped into the viewport's coordinate
space, but both of these mappings use the updated scroll offset.)

This is a temporary fix until we figure out a better way to detect real
layout janks in fixed or sticky elements.

Bug: 581518
Change-Id: I405c0933eb3cd52c135e97db55cb72c32dedc1a6
Reviewed-on: https://chromium-review.googlesource.com/c/1430589
Commit-Queue: Steve Kobes <skobes@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625370}
2 files changed