Supports growing non-COW JSArray by a single element if the backing store has room, and initial allocation of a backing store for the store to index zero of an empty array  to kPreallocatedArrayElements elements (e.g. the [] array literal).

Review URL: https://chromiumcodereview.appspot.com/9310117

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10673 ce2b1a6d-e550-0410-aec6-3dcde31c8c00