ES6: Add support for method shorthand in object literals

This is governed by the harmony-object-literals flag.

BUG=v8:3516
LOG=Y
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/477263002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23846 ce2b1a6d-e550-0410-aec6-3dcde31c8c00