CPU profiler: make code events handling scalable.

CPU profiler: make code events handling scalable.

I changed the implementation of a queue between the VM and processor
thread to be unbounded and lock-free, using Herb Sutter's example from
DDJ article: http://www.ddj.com/high-performance-computing/210604448
This had brought back profiling overhead to a minimum for the page
from Chromium's issue 16184.

BUG=714

Review URL: http://codereview.chromium.org/2091019

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4706 ce2b1a6d-e550-0410-aec6-3dcde31c8c00