Simulator specific code that is the same on all platforms as well as TickSample instance retrieval extracted into SampleHelper class.

Drive-by: extracted platform-independent pieces of Sampler::PlatformData into PlatformDataCommon.

BUG=None
R=loislo@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/15957005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14910 ce2b1a6d-e550-0410-aec6-3dcde31c8c00