Implement video frame acknowledgements in the chromoting protocol.
Added frame_id field in the VideoPacket message. Client now acknowledges
every frame that has frame_id set by sending VideoAck messages after
the corresponding frame is decoded and rendered.
On the host the VideoAck messages are processed by the new
VideoFeedbackStub, which is implemented in CaptureScheduler.
CaptureScheduler limits number of unacknowledged frames to 4. This
number was chosen experimentally to minimize latency (using
remoting_perftests).
BUG=448838
Review URL: https://codereview.chromium.org/850983002
Cr-Commit-Position: refs/heads/master@{#317824}
18 files changed
