GitLab

The "empty" line box is what CSS defines as "certain zero-
height line box", that suffices certain conditions as defined
in the spec and is ignored for margin collapsing.

It has some special behaviors, such as to ignore strut, that
LayoutNG suppressed to generate their child fragments.
However, we need them under certain conditions such as when
they have out-of-flow container as descendants.

This change breaks some normal flow, out-of-flow, and outline
tests.

Normal flow failures were fixed by adding an explicit
|IsEmptyLineBox()| function.

Out-of-flow failures are fixed as a separate CL in r610994
(CL:1351189).

Outline failures are fixed in this CL and in r611954
(CL:13543199) thanks to atotic@.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I4d393af016439cdbe085d91fdd1e8550d320d1f1
Bug: 636993, 903578
Reviewed-on: https://chromium-review.googlesource.com/c/1251142
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Aleks Totic <atotic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612108}