[DL] Handle forced layouts.

If the layout is forced, then we temporarily allow the processing of
the subtree. The locked element's frame rect still remains to be the same
as at the time the lock was acquired.

R=chrishtr@chromium.org, mstensho@chromium.org, futhark@chromium.org

Bug: 907613, 882663
Change-Id: I9d1f63c287a73e7a8f3cbc9cb5acc2a009ddd024
Reviewed-on: https://chromium-review.googlesource.com/c/1363957
Commit-Queue: vmpstr <vmpstr@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615556}
4 files changed