Version 3.28.6 (based on bleeding_edge revision r22068)

Unbreak "os" stuff in shared d8 builds (issue 3407).

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@22071 ce2b1a6d-e550-0410-aec6-3dcde31c8c00