Add missing null pointer check in HTMLCanvasElement.cpp

Add missing null pointer check in HTMLCanvasElement.cpp

Fixing an oversight from previous CL:
https://codereview.chromium.org/2594093002/

BUG=676585
TBR=xlai@chromium.org

Committed: https://crrev.com/f24759eb82410ae9383cc527bb6aecb7f72d2747
Cr-Commit-Position: refs/heads/master@{#440509}

[Justin Novosad, 2016-12-22 19:11:47]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2016-12-22 19:12:15]

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, 2016-12-22 21:30:23]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1482433907792010, "parent_rev":
"2a4dd44d642137598ac50e6f80279ad7c54b5c4b", "commit_rev":
"56afad6a8a1fd8bbe4af6d749287203da5e60717"}

[commit-bot: I haz the power, 2016-12-22 21:30:49]

Description was changed from

==========
Add missing null pointer check in HTMLCanvasElement.cpp

Fixing an oversight from previous CL:
https://codereview.chromium.org/2594093002/

BUG=676585
TBR=xlai@chromium.org
==========

to

==========
Add missing null pointer check in HTMLCanvasElement.cpp

Fixing an oversight from previous CL:
https://codereview.chromium.org/2594093002/

BUG=676585
TBR=xlai@chromium.org

Review-Url: https://codereview.chromium.org/2598963004
==========

[commit-bot: I haz the power, 2016-12-22 21:30:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-12-22 21:34:45]

Description was changed from

==========
Add missing null pointer check in HTMLCanvasElement.cpp

Fixing an oversight from previous CL:
https://codereview.chromium.org/2594093002/

BUG=676585
TBR=xlai@chromium.org

Review-Url: https://codereview.chromium.org/2598963004
==========

to

==========
Add missing null pointer check in HTMLCanvasElement.cpp

Fixing an oversight from previous CL:
https://codereview.chromium.org/2594093002/

BUG=676585
TBR=xlai@chromium.org

Committed: https://crrev.com/f24759eb82410ae9383cc527bb6aecb7f72d2747
Cr-Commit-Position: refs/heads/master@{#440509}
==========

[commit-bot: I haz the power, 2016-12-22 21:34:46]

Patchset 1 (id:??) landed as
https://crrev.com/f24759eb82410ae9383cc527bb6aecb7f72d2747
Cr-Commit-Position: refs/heads/master@{#440509}