Reduce size of array in polymorph-arrays.js.

R=danno@chromium.org
BUG=

Review URL: https://codereview.chromium.org/686273003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25114 ce2b1a6d-e550-0410-aec6-3dcde31c8c00