Merged r18737 into 3.23 branch.

Fixed floor-of-div optimization.

BUG=334708
LOG=N
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/135903015

git-svn-id: https://v8.googlecode.com/svn/branches/3.23@18818 ce2b1a6d-e550-0410-aec6-3dcde31c8c00