Merged r19816 into trunk branch.

Revert "Enable Object.observe by default"

BUG=v8:2409
LOG=N
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/194973005

git-svn-id: https://v8.googlecode.com/svn/trunk@19817 ce2b1a6d-e550-0410-aec6-3dcde31c8c00