[layoutng] Add some LIKELY/UNLIKELY annotations

R=eae@chromium.org

Change-Id: Iedcf3f24205beea7a0de08f0544f745eb434404f
Reviewed-on: https://chromium-review.googlesource.com/c/1496439
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636677}
3 files changed