An optimization in the array constructor wasn't firing because the code
would check for constant values, failing to find them through
intervening HForceRepresentation instructions. Repaired this site. A
follow-on CL will provide a better way of making decisions based on
constant HValues.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/59623009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17708 ce2b1a6d-e550-0410-aec6-3dcde31c8c00