Do not start sampler thread when CpuProfiler is active

Do not start sampler thread when CpuProfiler is active

Now that CpuProfiler sends does sampling on the profile event processing thread there is no need to launch sampler thread. The latter is used only for --prof profiler.

BUG=v8:2814
R=bmeurer@chromium.org, svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16430

[yurys, 2013-08-21 08:40:45]

ping

[Sven Panne, 2013-08-21 10:07:16]

LGTM if we have test cases for this (I'm relatively sure about this for the
CpuProfiler, but not about tests for --prof).

[yurys, 2013-08-23 06:32:19]

On 2013/08/21 10:07:16, Sven Panne wrote:
> LGTM if we have test cases for this (I'm relatively sure about this for the
> CpuProfiler, but not about tests for --prof).

I don't think we have tests for --prof except those for the tick-processor
scripts. I tested it manually though and it worked fine.

Also I'm thinking about disabling CpuProfiler when --prof is used. That would
simplify the profiling logic. I can't imaging a valid use case when we would
need both working simultaneously.

[Benedikt Meurer, 2013-08-27 13:58:11]

LGTM

[yurys, 2013-08-29 14:04:05]

Committed patchset #2 manually as r16430 (presubmit successful).