Update XServerPixelBuffer to handle errors returned from XGetImage().

Update XServerPixelBuffer to handle errors returned from XGetImage().

XGetImage() may return NULL and XServerPixelBuffer wasn't handling this
case properly.

BUG=649487
Committed: https://crrev.com/4a18f16c62975e21ab3db9eb7a3812220ee6b3c6
Cr-Commit-Position: refs/heads/master@{#14754}

[Sergey Ulanov, 2016-10-24 21:04:36]

sergeyu@chromium.org changed reviewers:
+ gyzhou@chromium.org

[GeorgeZ, 2016-10-24 21:35:08]

On 2016/10/24 21:04:36, Sergey Ulanov wrote:

lgtm

[Sergey Ulanov, 2016-10-24 21:38:05]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2016-10-24 21:38:14]

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, 2016-10-24 22:45:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-24 22:45:56]

Description was changed from

==========
Update XServerPixelBuffer to handle errors returned from XGetImage().

XGetImage() may return NULL and XServerPixelBuffer wasn't handling this
case properly.

BUG=649487
==========

to

==========
Update XServerPixelBuffer to handle errors returned from XGetImage().

XGetImage() may return NULL and XServerPixelBuffer wasn't handling this
case properly.

BUG=649487

Committed: https://crrev.com/4a18f16c62975e21ab3db9eb7a3812220ee6b3c6
Cr-Commit-Position: refs/heads/master@{#14754}
==========

[commit-bot: I haz the power, 2016-10-24 22:45:57]

Patchset 1 (id:??) landed as
https://crrev.com/4a18f16c62975e21ab3db9eb7a3812220ee6b3c6
Cr-Commit-Position: refs/heads/master@{#14754}