Tighten object verification.

Often, when we call MaybeObject::Verify, what we want is Object::ObjectVerify.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/218993005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20382 ce2b1a6d-e550-0410-aec6-3dcde31c8c00