[LayoutNG] Fix text-indent with negative values in RTL.

This allows NGLineInfo to return a Width which isn't clamped to zero
for negative values.

This allows alignment of text to work correctly for these values.
Additionally, when adjusting the inline static position of abs-pos
children, we use the resulting fragment inline size, instead of the
line width, as this may be different.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I0876f148d285147c3b5cec658ebd7831e97b11aa
Bug: 	636993
Reviewed-on: https://chromium-review.googlesource.com/1147875
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577789}
5 files changed