Initial support for nested multicol layout.
Nested column balancing doesn't work yet. Also no support for mapping visual
points to flow thread points (which is used by a few operations, but not by the
most common ones, like painting and hit-testing).
There are other corner-cases to sort out, too.
Still no support for printing multicol documents, but that's the ultimate goal
of this work.
BUG=447718
R=jchaffraix@chromium.org,leviw@chromium.org
Review URL: https://codereview.chromium.org/1292163002
git-svn-id: svn://svn.chromium.org/blink/trunk@200639 bbb929c8-8fbe-4397-9dbb-9b2b20218538
12 files changed
