MIPS: Fix for bug 245480. Calling new Array(a) with a single argument could result in creating a holey array with a packed elements kind.

Port r15095 (4a97e1e4)

BUG=

Review URL: https://codereview.chromium.org/16861003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15104 ce2b1a6d-e550-0410-aec6-3dcde31c8c00