[LayoutNG] Remove LineData member from NGLineBreaker.

I remember we had a conversation about this at some stage, when a
single NGLineBreaker instance was being re-used for multiple lines,
(so we could easily reset the state).

It doesn't seem like we'll go back to this (reusing for multiple lines)
and removing this seems likes it simplifies a few things.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I48248f3bf871fbb3eda6aaebe0786f7a61d3f390
Reviewed-on: https://chromium-review.googlesource.com/1139104
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575552}
5 files changed