Support factoring per-frame max move distance into layout shift.

This change exposes layout shift and cumulative scores with
per-frame max move distance factored in via tracing, so we can
better understand the impact such a change would have and see
if it results in a net improvement.

Bug: 962962
Change-Id: I55d9e5fdcc0abb1e66b7f42fe13f793d0851159e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611103
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Bryan McQuade <bmcquade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661431}
3 files changed