Version 3.28.64 (based on bleeding_edge revision r23004)

ES6: Implement WeakMap and WeakSet constructor logic (issue 3399).

Enable ES6 unscopables (issue 3401).

Turn on harmony_unscopables for es_staging (issue 3401).

Remove proxies from --harmony switch for M38, because problems.

Reland "Add initial support for compiler unit tests using GTest/GMock." (issue 3489).

Enable ES6 iteration by default (issue 2214).

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@23007 ce2b1a6d-e550-0410-aec6-3dcde31c8c00