There was an obvious bug with missing call to SamplerRegistry::GetState.
I've also updated CpuProfiler to avoid stopping sampler, if it didn't started it.

R=vitalyr@chromium.org
BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6712062

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7293 ce2b1a6d-e550-0410-aec6-3dcde31c8c00