mash: Fix mash in debug builds.

mash: Fix mash in debug builds.

X11EventSource::GetInstance() would DCHECK if it had no instance. Add a
dedicated bool returning checker function and use it where we were
crashing.

BUG=594600
Committed: https://crrev.com/fd1cc4c7b4cb560f2fd7d23ac9f4ebf005f88e44
Cr-Commit-Position: refs/heads/master@{#395125}

[Elliot Glaysher, 2016-05-20 18:10:45]

erg@chromium.org changed reviewers:
+ sadrul@chromium.org

[sadrul, 2016-05-20 18:14:36]

thanks. lgtm

[Elliot Glaysher, 2016-05-20 18:15:31]

The CQ bit was checked by erg@chromium.org

[commit-bot: I haz the power, 2016-05-20 18:15:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2004533002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2004533002/1

[commit-bot: I haz the power, 2016-05-20 18:23:12]

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

[commit-bot: I haz the power, 2016-05-20 18:23:13]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[Elliot Glaysher, 2016-05-20 18:25:31]

erg@chromium.org changed reviewers:
+ sky@chromium.org

[Elliot Glaysher, 2016-05-20 18:25:32]

+sky for OWNERS stamp

[sky, 2016-05-20 18:27:32]

LGTM

[Elliot Glaysher, 2016-05-20 18:30:57]

The CQ bit was checked by erg@chromium.org

[commit-bot: I haz the power, 2016-05-20 18:31:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2004533002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2004533002/1

[commit-bot: I haz the power, 2016-05-20 18:58:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-20 18:59:53]

Description was changed from

==========
mash: Fix mash in debug builds.

X11EventSource::GetInstance() would DCHECK if it had no instance. Add a
dedicated bool returning checker function and use it where we were
crashing.

BUG=594600
==========

to

==========
mash: Fix mash in debug builds.

X11EventSource::GetInstance() would DCHECK if it had no instance. Add a
dedicated bool returning checker function and use it where we were
crashing.

BUG=594600

Committed: https://crrev.com/fd1cc4c7b4cb560f2fd7d23ac9f4ebf005f88e44
Cr-Commit-Position: refs/heads/master@{#395125}
==========

[commit-bot: I haz the power, 2016-05-20 18:59:54]

Patchset 1 (id:??) landed as
https://crrev.com/fd1cc4c7b4cb560f2fd7d23ac9f4ebf005f88e44
Cr-Commit-Position: refs/heads/master@{#395125}