Version 3.28.60 (based on bleeding_edge revision r22894)

Enable ES6 Map and Set by default (issue 1622).

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@22897 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/trunk' into trunk