Fix crash in WebAXObject::showContextMenu

Fix crash in WebAXObject::showContextMenu

It was crashing if given the document node because it's not an element and
it has no parent.

BUG=631807
Committed: https://crrev.com/b219d03ce85fc738a0bd8054395af4f03ad02544
Cr-Commit-Position: refs/heads/master@{#409817}

[dmazzoni, 2016-08-02 18:03:22]

dmazzoni@chromium.org changed reviewers:
+ mkwst@chromium.org

[dmazzoni, 2016-08-02 18:03:29]

The CQ bit was checked by dmazzoni@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-02 18:04:22]

Dry run: 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, 2016-08-02 22:02:39]

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

[commit-bot: I haz the power, 2016-08-02 22:02:40]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[Mike West, 2016-08-04 12:42:15]

LGTM

[dmazzoni, 2016-08-04 15:42:30]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2016-08-04 15:43:09]

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, 2016-08-04 17:12:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-04 17:15:01]

Description was changed from

==========
Fix crash in WebAXObject::showContextMenu

It was crashing if given the document node because it's not an element and
it has no parent.

BUG=631807
==========

to

==========
Fix crash in WebAXObject::showContextMenu

It was crashing if given the document node because it's not an element and
it has no parent.

BUG=631807

Committed: https://crrev.com/b219d03ce85fc738a0bd8054395af4f03ad02544
Cr-Commit-Position: refs/heads/master@{#409817}
==========

[commit-bot: I haz the power, 2016-08-04 17:15:03]

Patchset 1 (id:??) landed as
https://crrev.com/b219d03ce85fc738a0bd8054395af4f03ad02544
Cr-Commit-Position: refs/heads/master@{#409817}