This is a first refactoring towards lazily allocating our layers as part of bug 75568. Once all callers go through this new method we can add some layer() checks without having to patch all the call sites.
Created attachment 123868 [details] Proposed refactoring.
Created attachment 127636 [details] Updated change, moved scrolledContentOffset down to RenderBox.
Created attachment 128003 [details] Fixed small typo (LayoutSize vs IntSize).
Comment on attachment 128003 [details] Fixed small typo (LayoutSize vs IntSize). r=me
Committed r108382: <http://trac.webkit.org/changeset/108382>