[layoutng] Make sure to force child layout for the legacy/ng interop

We need to force this because the override size may have changed since
last time.

R=eae@chromium.org,mstensho@opera.com,glebl@chromium.org
BUG=635619

Review-Url: https://codereview.chromium.org/2353423002
Cr-Commit-Position: refs/heads/master@{#420159}
1 file changed