Version 3.21.7

Fixed casts of eternal handles.

Turned on global handle zapping.

Always visit branches during HGraph building (Chromium issue 280333).

Profiler changes: removed deprecated API, support higher sampling rate on Windows.

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@16446 ce2b1a6d-e550-0410-aec6-3dcde31c8c00