Load elimination fix with a test case.

R=titzer@chromium.org, verwaest@chromium.org

Review URL: https://codereview.chromium.org/143413019

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18884 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Flow engine fixes: unreachable block processing, state merging.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/144013003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18885 ce2b1a6d-e550-0410-aec6-3dcde31c8c00