These accessors also always call into C++ anyways, so there's no point
in having the JavaScript wrappers.

R=yangguo@chromium.org
BUG=v8:5049, chromium:655963

Committed: https://crrev.com/ede69cfabd790fe9f171b5d1f426ea0fc55e3c98
Review-Url: https://codereview.chromium.org/2417183002
Cr-Original-Commit-Position: refs/heads/master@{#40298}
Cr-Commit-Position: refs/heads/master@{#40306}