SmartPointer doesn't have -> operator and conversion to bool.

This a quick fix, I'll try to add -> operator with a separate CL.

TBR=mnaganov@chromium.org

Review URL: http://codereview.chromium.org/1969005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4594 ce2b1a6d-e550-0410-aec6-3dcde31c8c00