Don't ignore SIGABRT sent by the kernel

Don't ignore SIGABRT sent by the kernel

This makes the exception handler treat a SIGABRT generated by
the kernel in same way as one generated internally.

SIGABRT can be generated internally (typically by calling abort(),
but also with signal()) but it can also be sent by the kernel, in
which case si_pid is 0.  The original code assumes that the signal
is sent again upon return, but that doesn't happen for SIGABRT,
so the signal is lost.

BUG=303075
TEST=tested with alt-volup-X on a chromebook

[Luigi Semenzato, 2013-11-01 18:38:28]

Are you folks the right reviewers for this?  Thanks!

[Mark Mentovai, 2013-11-01 20:09:41]

LGTM

[Mark Mentovai, 2013-11-01 20:10:19]

I don’t know why this was sent to this codereview instance instead of
breakpad.appspot.com with a cc to google-breakpad-dev.

[Luigi Semenzato, 2013-11-01 20:13:25]

On 2013/11/01 20:10:19, Mark Mentovai wrote:
> I don’t know why this was sent to this codereview instance instead of
> http://breakpad.appspot.com with a cc to google-breakpad-dev.

Should I move it over?

I have no idea where it belongs, I just followed the Chromium instructions.

[Luigi Semenzato, 2013-11-01 20:17:01]

On 2013/11/01 20:13:25, semenzato1 wrote:
> On 2013/11/01 20:10:19, Mark Mentovai wrote:
> > I don’t know why this was sent to this codereview instance instead of
> > http://breakpad.appspot.com with a cc to google-breakpad-dev.
> 
> Should I move it over?
> 
> I have no idea where it belongs, I just followed the Chromium instructions.

In any case, I realized I can't commit this without more digging.  I am not sure
that abort() will work from all threads with these changes.

Dave, are you familiar with this?  Thanks!

[Mark Mentovai, 2013-11-01 20:42:27]

When you wind up seeking another review, you should do it on Breakpad’s
codereview instance, which will send the review request to the
google-breakpad-dev mailing list. You should be subscribed (e-mail off is OK) to
google-breakpad-dev.

The breakpad imported into Chrome seems to be missing the codereview.settings
file that sets this up correctly. If you svn checkout svn checkout
http://google-breakpad.googlecode.com/svn/trunk/, you should get the whole
thing.