Add support for printing multicol containers, and enable it.
Introduce an abstract class FragmentationContext, which is either implemented
by LayoutMultiColumnFlowThread for multicol, or by the new
ViewFragmentationContext class, which is attached to a LayoutView when
printing. This way it will act as an enclosing fragmentation context for a
multicol container in the document. This is similar to how an outer multicol
container acts as an enclosing fragmentation context for an inner multicol
container.
The multicol flow thread implementation will now obtain and use a
FragmentationContext when attempting to locate its enclosing fragmentation
context, rather than only looking for another flowthread up there (and assume
that it's not nested if none was found). A big part of this CL is to teach the
multicol implementation about this, which means that there are quite a few
mechanical changes from enclosingFlowThread() (and LayoutMultiColumnFlowThread
method calls) to enclosingFragmentationContext() (and FragmentationContext
method calls).
Replaced an old printing test that tested that multicol didn't work, with one
that tests that multicol does work. :)
Also added another test that splits a multicol container over two pages.
BUG=99358
R=leviw@chromium.org
Review URL: https://codereview.chromium.org/1492143002
Cr-Commit-Position: refs/heads/master@{#363838}
20 files changed
