BUG=148757
TEST=largeObj test from the bug is 2x faster.
R=yangguo@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11377100

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12938 ce2b1a6d-e550-0410-aec6-3dcde31c8c00