Improve test-cpu-profiler.cc tests stability

Improve test-cpu-profiler.cc tests stability

The tests sometimes fail on bots as they don't have time to collect enough samples. This change makes them use counter of samples taken when v8 is either in JS or EXTERNAL state and repeat sampling until desired threshold is reached.

BUG=v8:2628
R=loislo@chromium.org, yangguo@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=15592

[loislo, 2013-07-04 14:14:42]

lgtm

[Yang, 2013-07-04 14:59:19]

On 2013/07/04 14:14:42, loislo wrote:
> lgtm

As far as I can see, the counter's sole purpose is for the tests. Would it be
possible to do the counting in the tests, even if it's more expensive?

[yurys, 2013-07-04 16:28:42]

On 2013/07/04 14:59:19, Yang wrote:
> On 2013/07/04 14:14:42, loislo wrote:
> > lgtm
> 
> As far as I can see, the counter's sole purpose is for the tests. Would it be
> possible to do the counting in the tests, even if it's more expensive?

I see two options:
1) Have a flag on the sampler whether to count samples and turn it on only in
tests.
2) Make Sampler dispatch tick event notification to its listeners and implement
the counter in the tests.

Do any of them make sense to you?

Note that this code has always been there just for the testing purpose (though
it is unused at the moment).

[yurys, 2013-07-05 12:11:11]

On 2013/07/04 16:28:42, Yury Semikhatsky wrote:
> On 2013/07/04 14:59:19, Yang wrote:
> > On 2013/07/04 14:14:42, loislo wrote:
> > > lgtm
> > 
> > As far as I can see, the counter's sole purpose is for the tests. Would it
be
> > possible to do the counting in the tests, even if it's more expensive?
> 
> I see two options:
> 1) Have a flag on the sampler whether to count samples and turn it on only in
> tests.
> 2) Make Sampler dispatch tick event notification to its listeners and
implement
> the counter in the tests.
> 
> Do any of them make sense to you?
> 
> Note that this code has always been there just for the testing purpose (though
> it is unused at the moment).

Added Sampler::is_counting_samples_ flag which is true only in tests. PTAL

[yurys, 2013-07-09 18:40:10]

Yang, could you take another look?

[Yang, 2013-07-10 08:35:41]

On 2013/07/09 18:40:10, Yury Semikhatsky wrote:
> Yang, could you take another look?

The flag option looks good.

LGTM.

[loislo, 2013-07-10 12:57:07]

Committed patchset #3 manually as r15592 (presubmit successful).