Profiler is now started from JavaScript. Since we always capture stack trace when starting profiler there should always be at least one expected sample in the profile.

Also changed ProfilerEventsProcessor::AddCurrentStack to make sure it call TickSample::Init to instead of custom initialization code.

BUG=v8:2920
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/25686011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17140 ce2b1a6d-e550-0410-aec6-3dcde31c8c00