Fix cornercase in r19475

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/169353003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19480 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Bugfix in check elimination with a regression test.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/172173003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19481 ce2b1a6d-e550-0410-aec6-3dcde31c8c00