When a data channel fails to be created, return nil instead of crashing.

When a data channel fails to be created, return nil instead of crashing.

BUG=webrtc:4619
Review-Url: https://codereview.webrtc.org/2860353002
Cr-Commit-Position: refs/heads/master@{#18034}
Committed: https://chromium.googlesource.com/external/webrtc/+/299c8e0161960db39385e50f364834dd02e8ded7

[Taylor Brandstetter, 2017-05-05 08:35:49]

deadbeef@webrtc.org changed reviewers:
+ magjed@webrtc.org

[Taylor Brandstetter, 2017-05-05 08:35:49]

PTAL

[magjed_webrtc, 2017-05-05 09:40:58]

lgtm

[Taylor Brandstetter, 2017-05-05 16:35:26]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-05-05 16:35:28]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2017-05-05 17:00:19]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1494002126121550, "parent_rev":
"a780cab3a5ebe17763f064bd0b90310d32ebc367", "commit_rev":
"299c8e0161960db39385e50f364834dd02e8ded7"}

[commit-bot: I haz the power, 2017-05-05 17:00:22]

Description was changed from

==========
When a data channel fails to be created, return nil instead of crashing.

BUG=webrtc:4619
==========

to

==========
When a data channel fails to be created, return nil instead of crashing.

BUG=webrtc:4619

Review-Url: https://codereview.webrtc.org/2860353002
Cr-Commit-Position: refs/heads/master@{#18034}
Committed:
https://chromium.googlesource.com/external/webrtc/+/299c8e0161960db39385e50f3...
==========

[commit-bot: I haz the power, 2017-05-05 17:00:22]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/299c8e0161960db39385e50f3...