Complete layout even if a block needs relayout due to widows or column balancing.

We cannot just abort in the middle of layoutBlockFlow() when we detect that we
need another layout pass (due to new column height or because we want an
earlier break to satisfy the widows requirement). We might miss our only
opportunity to detect size changes that way, and thus skip necessary layout and
repositioning of absolutely positioned descendants.

BUG=591637

Review-Url: https://codereview.chromium.org/2471623003
Cr-Commit-Position: refs/heads/master@{#436192}
5 files changed