Short-term fix for Aura Desktop/Window capture.

Short-term fix for Aura Desktop/Window capture.

The compositor is not reliably calling the OnCompositingEnded() observer
method, causing capture to "freeze." However, it's not clear that
AuraWindowCaptureMachine should have been using it to trigger copy
requests in the first place. This change switches over to using the only
other reliable feedback mechanism available (as of this writing). That
is, we now use the OnAnimationStep() observer method as a trigger to
initiate copy requests.

Long-term, we need a better observer callback interface from the
compositor for this use case. The solution here will always capture
frames at the maximum framerate, which means CPU/GPU is being wasted on
redundant captures, and the quality/smoothness of animating content will
suffer significantly.

BUG=492839, 600031
Committed: https://crrev.com/1ca25389bc07e4cb43ccc46af8159b0291c7e5d5
Cr-Commit-Position: refs/heads/master@{#390156}

[miu, 2016-04-27 04:35:34]

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

[miu, 2016-04-27 04:35:34]

gyzhou: PTAL. This will fix crbug 600031, but I'm not terribly happy with this.
I would rather fix this problem the right way, but I don't have the cycles to
spare on it right now. If you want to take this on, let me know and we can meet
to discuss a "long-term, non-hacky" solution. Please see the change description,
and the comments I added at the end of aura_window_capture_machine.cc for more
details.

[GeorgeZ, 2016-04-27 16:44:34]

Miu,

LGTM with a nit.

I tested on Device blaze. The issue is solved thought captured video is not very
smooth as you expected.

I was asked to shift my focus to a new project from desktop capture recently.

George

https://codereview.chromium.org/1922143004/diff/1/content/browser/media/captu...
File content/browser/media/capture/aura_window_capture_machine.cc (right):

https://codereview.chromium.org/1922143004/diff/1/content/browser/media/captu...
content/browser/media/capture/aura_window_capture_machine.cc:86: }
The function may return false if host or compositor is nullptr.

[miu, 2016-04-27 19:01:24]

Thanks George.  Added the early return as you suggested:

https://codereview.chromium.org/1922143004/diff/1/content/browser/media/captu...
File content/browser/media/capture/aura_window_capture_machine.cc (right):

https://codereview.chromium.org/1922143004/diff/1/content/browser/media/captu...
content/browser/media/capture/aura_window_capture_machine.cc:86: }
On 2016/04/27 16:44:34, GeorgeZ wrote:
> The function may return false if host or compositor is nullptr.

Done.

[miu, 2016-04-27 19:01:29]

The CQ bit was checked by miu@chromium.org

[miu, 2016-04-27 19:01:29]

The patchset sent to the CQ was uploaded after l-g-t-m from gyzhou@chromium.org
Link to the patchset: https://codereview.chromium.org/1922143004/#ps20001
(title: "Return false on missing compositor in InternalStart().")

[commit-bot: I haz the power, 2016-04-27 19:02:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1922143004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1922143004/20001

[commit-bot: I haz the power, 2016-04-27 19:57:41]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-30 17:12:13]

Patchset 2 (id:??) landed as
https://crrev.com/1ca25389bc07e4cb43ccc46af8159b0291c7e5d5
Cr-Commit-Position: refs/heads/master@{#390156}

[commit-bot: I haz the power, 2016-04-30 17:51:23]

Description was changed from

==========
Short-term fix for Aura Desktop/Window capture.

The compositor is not reliably calling the OnCompositingEnded() observer
method, causing capture to "freeze." However, it's not clear that
AuraWindowCaptureMachine should have been using it to trigger copy
requests in the first place. This change switches over to using the only
other reliable feedback mechanism available (as of this writing). That
is, we now use the OnAnimationStep() observer method as a trigger to
initiate copy requests.

Long-term, we need a better observer callback interface from the
compositor for this use case. The solution here will always capture
frames at the maximum framerate, which means CPU/GPU is being wasted on
redundant captures, and the quality/smoothness of animating content will
suffer significantly.

BUG=492839,600031
==========

to

==========
Short-term fix for Aura Desktop/Window capture.

The compositor is not reliably calling the OnCompositingEnded() observer
method, causing capture to "freeze." However, it's not clear that
AuraWindowCaptureMachine should have been using it to trigger copy
requests in the first place. This change switches over to using the only
other reliable feedback mechanism available (as of this writing). That
is, we now use the OnAnimationStep() observer method as a trigger to
initiate copy requests.

Long-term, we need a better observer callback interface from the
compositor for this use case. The solution here will always capture
frames at the maximum framerate, which means CPU/GPU is being wasted on
redundant captures, and the quality/smoothness of animating content will
suffer significantly.

BUG=492839,600031

Committed: https://crrev.com/1ca25389bc07e4cb43ccc46af8159b0291c7e5d5
Cr-Commit-Position: refs/heads/master@{#390156}
==========