Fall back to generic on access checks in JSON.stringify.

BUG=259366
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/18225006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15641 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Test case for missing access checks in object observe.

BUG=v8:2778
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/18794003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15642 ce2b1a6d-e550-0410-aec6-3dcde31c8c00