Need to remove line pagination struts when no longer fragmented.

We only used to recalculate pagination struts on lines when we were inside a
fragmentation context, but if said fragmentation context ceases to be one, we
need one final strut recalculation pass, to get rid of them all.

BUG=658019

Review-Url: https://codereview.chromium.org/2460673002
Cr-Commit-Position: refs/heads/master@{#428161}
4 files changed