Propogate status setting for profiler to track parents

Propogate status setting for profiler to track parents

[Reland: https://src.chromium.org/viewvc/chrome?view=rev&revision=120789
with minor change to avoid race on status change.]

This allows child processes to track ancestry, and report
it to the browser process.

Parent tracking is only turned on based on an 
environment variable.

r=rtenneti
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=121491

[jar (doing other things), 2012-02-08 01:00:48]

Raman: This is what you reviewed, with the status change pushed inside the if
statement as we discussed.

Jam: This is what you reviewed, with a lint correction on my non-alphabetic
ordering of the includes.

In both cases, the first upload is *exactly* what you reviewed.  Hence, you can
just look at the deltas from that upload.

[jam, 2012-02-10 19:25:13]

content lgtm