Improve the fix for r18344.

Our toolchains differ in mysterious ways, especially regarding
overloading resolution, templates, etc. :-P This fix avoids a
call/return just for resolution and uses a static_cast instead.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/118183002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18349 ce2b1a6d-e550-0410-aec6-3dcde31c8c00