be careful to merge feedback appropriately. For example, one array may
have gone holey, and then another allocated at the same place instead
went DOUBLE but remained packed. In this case the ElementsKind
ultimately stored in the AllocationSite should be HOLEY_DOUBLE.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/18531007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15629 ce2b1a6d-e550-0410-aec6-3dcde31c8c00