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
Review-Url: https://codereview.chromium.org/1922143004
Cr-Commit-Position: refs/heads/master@{#390156}
(cherry picked from commit 1ca25389bc07e4cb43ccc46af8159b0291c7e5d5)

Committed: https://chromium.googlesource.com/chromium/src/+/fdd26756b02ce6ae3b70ed99ce25155695f74b9e

[miu, 2016-04-29 23:38:23]

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

Review-Url: https://codereview.chromium.org/1922143004
Cr-Commit-Position: refs/heads/master@{#390156}
(cherry picked from commit 1ca25389bc07e4cb43ccc46af8159b0291c7e5d5)
==========

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

Review-Url: https://codereview.chromium.org/1922143004
Cr-Commit-Position: refs/heads/master@{#390156}
(cherry picked from commit 1ca25389bc07e4cb43ccc46af8159b0291c7e5d5)

Committed:
https://chromium.googlesource.com/chromium/src/+/fdd26756b02ce6ae3b70ed99ce25...
==========

[miu, 2016-04-29 23:38:24]

Committed patchset #1 (id:1) manually as
fdd26756b02ce6ae3b70ed99ce25155695f74b9e.