Make LayoutState not arena-allocated.
<https://webkit.org/b/122649>

Reviewed by Antti Koivisto.

Let RenderView own a singly-linked chain of LayoutState objects
managed by unique_ptr.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157336 268f45cc-cd09-0410-ab3c-d52691b4dbfc
5 files changed