Add sanity test for CPU profiler

The new test checks full CPU profiling cycle: using public
V8 API it starts profiling, executes a script, stops profiling
and analyzes collected profile to check that its top-down
tree has expected strutcture. The script that is being profiled
is guaranteed to run > 200ms to make sure enough samples
are collected.

To avoid possible flakiness due to non-deterministic time required
to start new thread on varios OSs when Sampler and ProfilerEventsProcessor
threads are being started the main thread is blocked until the threads
are running.

Also I removed the heuristic in profile-generator.cc where we try
to figure out if the value on top of the sampled stack is return address
of some frameless stub invocation. The code periodically gives false positive
with the new test ending up in an extra node in the collected cpu profile.
After discussion with jkummerow@ we concluded that the logic is too fragile
and that we can address frameless stub invocations in a more reliable way
later should they have a noticeable effect on cpu profiling.

BUG=None

Review URL: https://codereview.chromium.org/13627002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14205 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Put common case first

This might fix a 2% regression that we might be observing for CL 14128.

R=verwaest@chromium.org
BUG=

Review URL: https://codereview.chromium.org/13811021

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14206 ce2b1a6d-e550-0410-aec6-3dcde31c8c00