We already disallowed observing the global proxy; now we also
disallow any observation of access-checked objects (regardless
of whether the access check would succeed or fail, since there's
not a good way to tell the embedder what kind of access is being
requested).

Also disallow Object.getNotifier for the same reasons.

BUG=chromium:531891
LOG=y

Review URL: https://codereview.chromium.org/1346813002

Cr-Commit-Position: refs/heads/master@{#30774}