Handle exceptions thrown by Array.observe machinery

BUG=chromium:417709
LOG=N
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/651323003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24646 ce2b1a6d-e550-0410-aec6-3dcde31c8c00