Incorrect beforeChild parent calculation in RenderRubyBase::moveChildren.

Incorrect beforeChild parent calculation in RenderRubyBase::moveChildren.
https://bugs.webkit.org/show_bug.cgi?id=80297

Reviewed by Julien Chaffraix.

Source/WebCore:

beforeChild might share the same anonymous block parent with other previous
siblings. Before moving the children across ruby bases, we need to make sure
to split the tree across the beforeChild correctly.

Test: fast/ruby/ruby-text-before-child-split.html

* rendering/RenderRubyBase.cpp:
(WebCore::RenderRubyBase::moveChildren):

LayoutTests:

Test passes if you see the inline continuation in the first ruby base and only the
simple text in the second ruby base.

* fast/ruby/ruby-text-before-child-split-expected.png: Added.
* fast/ruby/ruby-text-before-child-split-expected.txt: Added.
* fast/ruby/ruby-text-before-child-split.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@111714 268f45cc-cd09-0410-ab3c-d52691b4dbfc