Version 3.28.20 (based on bleeding_edge revision r22308)

Remove deprecate counter/histogram methods.

Fixed printing of external references (Chromium issue 392068).

Fix several issues with ES6 redeclaration checks (issue 3426).

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@22309 ce2b1a6d-e550-0410-aec6-3dcde31c8c00