Implement ES6 symbol registry and predefined symbols

R=mstarzinger@chromium.org, arv@chromium.org
BUG=
LOG=Y

Review URL: https://codereview.chromium.org/203243004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20118 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Reland "Throw exception on invalid string length instead of OOM."

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/199583007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20119 ce2b1a6d-e550-0410-aec6-3dcde31c8c00