Enable tracking of objects by default

Enable tracking of objects by default

This is a reland of accumulated patches including CLs
8414036, 8425010, 8425013, 8424013.

It fully enables tracking of objects, as seen in about:tracking
in teh release build.

The problem this had in its initaial landing centered on
Mac instability in base_unittest.  We were encountering crash
on exit of the tests, with a stack dump involving pthreads.


r=rtenneti
BUG=101856
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=108026

[jar (doing other things), 2011-10-31 20:51:17]

John,

Please review/approve the content change.  Raman will work on the broader review
me (he reviewed the previous landings).

Thanks in advance,

Jim

[jam, 2011-10-31 20:53:27]

content lgtm

[ramant (doing other things), 2011-10-31 21:22:33]

LGTM.

Changes seem to be same as what was reviewed before except for disabling it in
release version of Mac.

thanks,
raman

[ramant (doing other things), 2011-10-31 22:32:04]

lgtm