Re-enable Trap.SigSysAction test under tsan.

Re-enable Trap.SigSysAction test under tsan.

The reason of Trap.SigSysAction failure under TSAN was identified,
which was;
TSAN intercepts sigaction(), similar to MSAN. So, direct syscall
breaks its assumption. Fallback to sigaction() on TSAN.

TEST=Ran bots with tsan. Ran the failure test case with tsan=1 locally.
BUG=481297
Committed: https://crrev.com/1fd8cbbab5cfa292bbfd006a7878a2f102195f90
Cr-Commit-Position: refs/heads/master@{#327216}

[hidehiko, 2015-04-27 18:57:15]

hidehiko@chromium.org changed reviewers:
+ mdempsky@chromium.org

[hidehiko, 2015-04-27 18:57:15]

Thank you for review in advance,
- hidehiko

[mdempsky, 2015-04-27 19:04:37]

lgtm

Is there any chance that this affects other clang sanitizer modes too?  E.g.,
ASAN?

[hidehiko, 2015-04-27 19:18:27]

On 2015/04/27 19:04:37, mdempsky wrote:
> lgtm
> 
> Is there any chance that this affects other clang sanitizer modes too?  E.g.,
> ASAN?

IIUC, remaining sanitizers are ASAN and LSAN.

ASAN interecepts sigaction, but it does not inject any callback wrappers.
Instead, it just filters the signals based on ASAN configurations. So, direct
syscall should work on it (though it slightly changes the behavior).
LSAN does not intercept sigaction.

So I think it's ok. WDYT (especially about ASAN), Matthew?
- hidehiko

[mdempsky, 2015-04-27 19:36:59]

On 2015/04/27 19:18:27, hidehiko wrote:
> So I think it's ok. WDYT (especially about ASAN), Matthew?

SGTM.  I just wanted to check that we wouldn't have more revert+reland cycles
from the other sanitizers.

[hidehiko, 2015-04-28 01:28:18]

On 2015/04/27 19:36:59, mdempsky wrote:
> On 2015/04/27 19:18:27, hidehiko wrote:
> > So I think it's ok. WDYT (especially about ASAN), Matthew?
> 
> SGTM.  I just wanted to check that we wouldn't have more revert+reland cycles
> from the other sanitizers.

Thanks. So submitting.

[hidehiko, 2015-04-28 01:28:22]

The CQ bit was checked by hidehiko@chromium.org

[commit-bot: I haz the power, 2015-04-28 01:28:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1103263003/1

[commit-bot: I haz the power, 2015-04-28 01:32:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-28 01:33:33]

Patchset 1 (id:??) landed as
https://crrev.com/1fd8cbbab5cfa292bbfd006a7878a2f102195f90
Cr-Commit-Position: refs/heads/master@{#327216}