Change exception type to Object.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/227163008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20571 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Implement handlified String::Flatten.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/228093004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20572 ce2b1a6d-e550-0410-aec6-3dcde31c8c00