A GC-related bug has started showing up after r15060 that unfortunately
I haven't been able to reproduce.  Disable generators by default for the
Canary push.

R=danno@chromium.org
BUG=

Review URL: https://codereview.chromium.org/16638011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15065 ce2b1a6d-e550-0410-aec6-3dcde31c8c00