[layoutng] Store borders on fragments as well

This avoids recomputing them later.

Also, changes RunOldLayout to use legacy layout to
compute border/padding to store on the fragment,
which seems more correct.

R=eae@chromium.org

Bug: 635619
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Id659d7c92eae81431d8e75a26ac3973421afc3d0
Reviewed-on: https://chromium-review.googlesource.com/1169634
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582339}
12 files changed