Fix GetStackSample to check for nullptr

Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=

Committed: https://crrev.com/23a9405c592e07c6d29c4388b376526406ffc77d
Cr-Commit-Position: refs/heads/master@{#38952}

[john.yan, 2016-08-25 17:23:53]

Description was changed from

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=
==========

to

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=
==========

[john.yan, 2016-08-25 17:23:53]

jyan@ca.ibm.com changed reviewers:
+ bjaideep@ca.ibm.com, joransiu@ca.ibm.com

[john.yan, 2016-08-25 17:24:05]

PTAL

[jochen (gone - plz use gerrit), 2016-08-26 15:09:55]

lgtm

[john.yan, 2016-08-26 16:50:53]

On 2016/08/26 15:09:55, jochen wrote:
> lgtm

Thanks.

[john.yan, 2016-08-26 16:50:56]

The CQ bit was checked by jyan@ca.ibm.com

[commit-bot: I haz the power, 2016-08-26 16:51:00]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-26 17:16:14]

Description was changed from

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=
==========

to

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=
==========

[commit-bot: I haz the power, 2016-08-26 17:16:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-26 17:17:18]

Description was changed from

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=
==========

to

==========
Fix GetStackSample to check for nullptr

callback_entrypoint_address call could return nullptr and therefore
causes seg fault intermittently.

R=jochen@chromium.org, lpy@chromium.org, yangguo@chromium.org
BUG=

Committed: https://crrev.com/23a9405c592e07c6d29c4388b376526406ffc77d
Cr-Commit-Position: refs/heads/master@{#38952}
==========

[commit-bot: I haz the power, 2016-08-26 17:17:19]

Patchset 1 (id:??) landed as
https://crrev.com/23a9405c592e07c6d29c4388b376526406ffc77d
Cr-Commit-Position: refs/heads/master@{#38952}