Add OS::GetCurrentProcessId and prepend output from trace-gc with the current pid

Add OS::GetCurrentProcessId and prepend output from trace-gc with the current pid

BUG=none
TEST=manual

Committed: https://code.google.com/p/v8/source/detail?r=12032

[jochen (gone - plz use gerrit), 2012-03-21 09:05:30]

plz review

do you have some kind of trybots? I don't feel like compiling this on windows
myself

[Michael Starzinger, 2012-04-12 14:37:48]

There are several --trace-gc lines missing which do not get the PID prepended.
So this CL look incomplete.

[jochen (gone - plz use gerrit), 2012-07-02 11:48:00]

On 2012/04/12 14:37:48, Michael Starzinger wrote:
> There are several --trace-gc lines missing which do not get the PID prepended.
> So this CL look incomplete.

Updated the CL to include the missing changes

[Michael Starzinger, 2012-07-06 14:00:05]

General feedback: I think it would be good to introduce a PrintPID() or
PrintPIDPrefix() method in v8utils.cc that either automatically prepends the PID
or just prints the PID prefix.

[jochen (gone - plz use gerrit), 2012-07-09 07:32:31]

On 2012/07/06 14:00:05, Michael Starzinger wrote:
> General feedback: I think it would be good to introduce a PrintPID() or
> PrintPIDPrefix() method in v8utils.cc that either automatically prepends the
PID
> or just prints the PID prefix.

done

[Michael Starzinger, 2012-07-10 12:27:32]

LGTM. I'll land this for you.