[layoutng] Skip a flexbox optimization in LayoutNG

In LayoutNG, HasPercentHeightDescendants() does not produce correct results
and it is difficult to get it to produce correct results. Accordingly, let's
disable this optimization for now.

Bug: 635619, 839661
Change-Id: I766ea2fbea647eb9d0f3767b64788b678d328953
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Reviewed-on: https://chromium-review.googlesource.com/1043009
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556596}
2 files changed