This way if the type oracle says an unreachable clause has a non-smi
type, we can still emit optimized code instead of doing an early
bailout.

This change depends of Florian's r5970.

Review URL: http://codereview.chromium.org/5812005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6037 ce2b1a6d-e550-0410-aec6-3dcde31c8c00