Inlined IsFoundByRuntimeProbingOnly.

It is only used internally at a single place.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/265243004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21137 ce2b1a6d-e550-0410-aec6-3dcde31c8c00