[New Multicolumn] A renderer can't be both a parent and a sibling of another renderer.
In addChild(), beforeChild needs to be a descendant of the parent
that's attempting to insert a renderer.
When redirecting renderer insertion to a child
RenderMultiColumnFlowThread, update beforeChild if it's set to said
RenderMultiColumnFlowThread as well.
BUG=358597
R=leviw@chromium.org
Review URL: https://codereview.chromium.org/568443002
git-svn-id: svn://svn.chromium.org/blink/trunk@183315 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
