Array constructor shouldn't require a Cell, just an AllocationSite.

The Array constructor has a needless dependency on an input argument
that is a Cell. It uses this to walk through to an AllocationSite.
The dependency hampers future work. Instead, pass the AllocationSite
as input to the Array constructor.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/140963004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18716 ce2b1a6d-e550-0410-aec6-3dcde31c8c00