Suppresses leaks in tracked_objects.

Suppresses leaks in tracked_objects.
This change adds a rule that suppresses probably-intentional leaks caused by r108026 <http://crrev.com/108026>;.

TBR=jar
BUG=102327
TEST=make the "Linux Tests (valgrind)(2)" bot green.
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=108068

[Hironori Bono, 2011-11-01 03:15:20]

Greetings jar,

Is it possible to check if this leak is your intentional one?

Regards,

Hironori Bono

[jar (doing other things), 2011-11-01 03:55:15]

LGTM

http://codereview.chromium.org/8431023/diff/1/tools/valgrind/memcheck/suppres...
File tools/valgrind/memcheck/suppressions.txt (right):

http://codereview.chromium.org/8431023/diff/1/tools/valgrind/memcheck/suppres...
tools/valgrind/memcheck/suppressions.txt:5207:
fun:_ZN15tracked_objects10ThreadData29ShutdownSingleThreadedCleanupEb
This is an excellent example of a race to supress.

This Shutdown... function is *ONLY* called in unit tests, and hence it is
possible that other threads, lingering from previous tests, are racing to see
status as this unit test runs.  As a result, this is an artifact of the unit
test only, and will *NEVER* take place in Chrome (the browser). 

In addition, the examination of status (raced against the setting of status) is
inconsequential, as the code handles any of the status values, in any order,
over time.  Hence any read is old or new values is handled gracefully.

Bottom line: Totally benign race.

Thanks for adding this.