Check buffer_pool_ for null in VideoCaptureController::PostStopping.

Check buffer_pool_ for null in VideoCaptureController::PostStopping.
buffer_pool_lock_ is not needed on the UI thread for this test, but if the
camera started and stopped without an OnFrameInfo, then it's possible that
the buffer_pool_ was never created.

BUG=231723
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=203069

[ncarter (slow), 2013-05-16 00:07:41]

wjia, please have a look

[wjia(left Chromium), 2013-05-16 00:14:16]

https://chromiumcodereview.appspot.com/15070008/diff/1/content/browser/render...
File content/browser/renderer_host/media/video_capture_controller.cc (right):

https://chromiumcodereview.appspot.com/15070008/diff/1/content/browser/render...
content/browser/renderer_host/media/video_capture_controller.cc:658: if
((buffer_pool_ && buffer_pool_->IsAnyBufferHeldForConsumers()) ||
Should this check be also added for other cases (whenever buffer_pool_ is used)?

[ncarter (slow), 2013-05-16 00:32:31]

https://codereview.chromium.org/15070008/diff/1/content/browser/renderer_host...
File content/browser/renderer_host/media/video_capture_controller.cc (right):

https://codereview.chromium.org/15070008/diff/1/content/browser/renderer_host...
content/browser/renderer_host/media/video_capture_controller.cc:658: if
((buffer_pool_ && buffer_pool_->IsAnyBufferHeldForConsumers()) ||
On 2013/05/16 00:14:16, wjia wrote:
> Should this check be also added for other cases (whenever buffer_pool_ is
used)?

It wouldn't hurt, but it's certainly not necessary everywhere. An example is
VideoCaptureController::ReturnBuffer, where if we've got a buffer to return,
then it seems reasonable to infer that we've received the buffer_pool_.

I admit that I don't fully understand the invariants of the various state
machine states in this code. I'll take a deeper look for other similar problems.

[sheu, 2013-05-19 02:40:12]

Adding myself.  Seeing this working on desktop capture.

[wjia(left Chromium), 2013-05-29 17:30:26]

Is this patch still alive? We need a complete fix ASAP.

[ncarter (slow), 2013-05-30 01:26:16]

I added a new version that does checks everywhere, though for the most part I
think some of the new checks aren't strictly necessary.

[wjia(left Chromium), 2013-05-30 02:36:32]

lgtm. please merge it to M27 and M28. Thanks!

[commit-bot: I haz the power, 2013-05-30 02:39:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/nick@chromium.org/15070008/24001

[commit-bot: I haz the power, 2013-05-30 04:50:15]

Change committed as 203069