[layoutng] Make sure to update m_isSelfCollapsing after ng layout
This will otherwise cause assertion failures on many pages.
We could also compute this in ng code during margin collapsing and just set it
on the old object, but I'm not sure that would be worth it.
This and https://codereview.chromium.org/2337763005/ fixes most (but not all)
of the assertion failures during legacy/ng interop.
R=ikilpatrick@chromium.org,eae@chromium.org,glebl@chromium.org
BUG=635619
Review-Url: https://codereview.chromium.org/2340113003
Cr-Commit-Position: refs/heads/master@{#418703}
3 files changed
