Reland "Linux perf tool support update + refactoring." (r22146, fifth attempt)

Bringing the offending timer functions to the platform dependent files.

BUG=
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/367033002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22210 ce2b1a6d-e550-0410-aec6-3dcde31c8c00