Suppress keepalive thread leak in DM.

Suppress keepalive thread leak in DM.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/1e237385ecc5b62ac57fab48fd25cfabb3840ae2

[mtklein_C, 2015-03-14 14:53:49]

mtklein@chromium.org changed reviewers:
+ joshualitt@google.com

[mtklein_C, 2015-03-14 14:54:22]

The CQ bit was checked by mtklein@chromium.org

[commit-bot: I haz the power, 2015-03-14 14:54:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1006143002/1

[commit-bot: I haz the power, 2015-03-14 14:54:29]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-03-14 20:54 UTC

[commit-bot: I haz the power, 2015-03-14 20:54:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-14 20:54:33]

No LGTM from a valid reviewer yet. Please ask for an LGTM from a
full Skia committer from
https://skia.googlesource.com/skia/+/master/CQ_COMMITTERS

[joshualitt, 2015-03-15 03:00:49]

On 2015/03/14 20:54:33, I haz the power (commit-bot) wrote:
> No LGTM from a valid reviewer yet. Please ask for an LGTM from a
> full Skia committer from
> https://skia.googlesource.com/skia/+/master/CQ_COMMITTERS

lgtm, thought to be honest I'm not exactly sure how to read these suppressions. 
fun:_ZN8SkThreadC1EPFvPvES0_ does seem to be the function with the leak though.

[mtklein, 2015-03-16 13:52:56]

On 2015/03/15 03:00:49, joshualitt wrote:
> On 2015/03/14 20:54:33, I haz the power (commit-bot) wrote:
> > No LGTM from a valid reviewer yet. Please ask for an LGTM from a
> > full Skia committer from
> > https://skia.googlesource.com/skia/+/master/CQ_COMMITTERS
> 
> lgtm, thought to be honest I'm not exactly sure how to read these
suppressions. 
> fun:_ZN8SkThreadC1EPFvPvES0_ does seem to be the function with the leak
though.

The Memcheck:Leak line focuses down which types of errors we're suppressing. 
Valgrind can catch a bunch
of different problems, but we only want to shut up the leak.  Similarly,
match-leak-kinds filters that down a
little more to only suppress leaks of a particular (un)certainty, just like this
one is.

We're suppressing memory leaked that was allocated at a particular call stack. 
Working from the bottom up,
it says ignore anything allocated from main() -> dm_main() -> start_keepalive()
-> SkThread::SkThread().
The ... says, match any call stack here; we just want to make sure we're only
suppressing this particular thread
allocated in start_keepalive(), but don't really care the details of the actual
bytes SkThread::SkThread() leaks.

Things get complicated of course because you need to write C++ function names
with mangling.  Luckily,
passing --gen-suppressions=all will print out the most precise suppression it
can, then you can tweak and
generalize from there.

[mtklein, 2015-03-16 13:53:00]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-03-16 13:53:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1006143002/1

[commit-bot: I haz the power, 2015-03-16 13:59:22]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/1e237385ecc5b62ac57fab48fd25cfabb3840ae2