This implies that the return value of native getters is checked. The nice part
is that one can even see the name of the property in question in the abort
output when the check failed.

Under some circumstances even the return value of interceptors gets checked, but
I'm not 100% sure about this, because the interceptor code is basically tuned to
death.

The change seems to have very low overhead, so it might be feasible to keep this
check enabled unconditionally.

Review URL: https://chromiumcodereview.appspot.com/10918071
Patch from Sven Panne <svenpanne@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12446 ce2b1a6d-e550-0410-aec6-3dcde31c8c00