[LayoutNG] Change static position of inline abpos to flow relative

This patch:
1. Fixes out-of-flow static position to be flow relative,
   from line-relative.
2. Fixes bidi-reordering orders out-of-flow objects
   incorrectly.

The first fix has been a bug since the beginning, but most
RTL out-of-flow tests pass due to the second problem.

The second problem was introduced when we stopped inserting
an Object Replacement Character for out-of-flow, because it
creates a break opportunity but all 4 impls do not create
a break opportunity for out-of-flow. It wasn't a good idea
because bidi algorithm cannot resolve embedding levels
without a character that represents.

This fix will change break opportunities around out-of-flow
objects. We can fix it in NGLineBreaker if this turns out
to be a problem.

Bug: 848496
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I3f3c7b5a8ddf93cb4b9d6fce21ccc5e2b7623901
Reviewed-on: https://chromium-review.googlesource.com/1133106
Reviewed-by: Aleks Totic <atotic@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576799}
4 files changed