Add WebrtcCaptureScheduler interface.

remoting/protocol/webrtc_capture_scheduler.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_PROTOCOL_WEBRTC_CAPTURE_SCHEDULER_H_
+#define REMOTING_PROTOCOL_WEBRTC_CAPTURE_SCHEDULER_H_
+
+#include "base/callback_forward.h"
+#include "remoting/codec/webrtc_video_encoder.h"
+#include "third_party/webrtc/video_encoder.h"
+
+namespace remoting {
+namespace protocol {
+
+// An abstract interface for capture schedulers.
+class WebrtcCaptureScheduler {
+ public:
+  WebrtcCaptureScheduler() {}
+  virtual ~WebrtcCaptureScheduler() {}
+
+  // Starts the scheduler. |capture_callback| will be called whenever a new
+  // frame should be captured.
+  virtual void Start(const base::Closure& capture_callback) = 0;
+
+  // Pauses the scheduler.

[Irfan, 2016/09/14 20:01:29]

Pauses/Resumes ?

[Sergey Ulanov, 2016/09/16 00:02:47]

Done.

+  virtual void Pause(bool pause) = 0;
+
+  // Requests a key frame.
+  virtual void SetKeyFrameRequest() = 0;
+
+  // Sets network bitrate estimate.
+  virtual void SetTargetBitrate(int bitrate_kbps) = 0;
+
+  // Called after |frame| has been captured to get encoding parameters for the
+  // frame. Returns false is the frame should be dropped (e.g. when there are

[Irfan, 2016/09/14 20:01:29]

Returns false if 

[Sergey Ulanov, 2016/09/16 00:02:47]

Done.

+  // no changed), true otherwise.
+  virtual bool GetEncoderFrameParams(

[Irfan, 2016/09/14 20:01:29]

It is a bit strange to me that encoder params are being decided by the capture
scheduler.

[Sergey Ulanov, 2016/09/16 00:02:47]

The idea here is that frame scheduling logic shouldn't be separated from encoder
parameters, particularly for top-off. This also allows to pass frame duration
from the scheduler and the encoder doesn't have enough context to determine
duration.
Perhaps it should be called FrameScheduler, WDYT?

[Irfan, 2016/09/16 17:21:19]

sgtm

+      const webrtc::DesktopFrame& frame,
+      WebrtcVideoEncoder::FrameParams* params_out) = 0;
+
+  // Called after a frame has been encoded and passed to the sender.
+  virtual void OnFrameEncoded(

[Irfan, 2016/09/14 20:01:29]

I may be imagining, but did you recently add ability to get a callback when a
frame is actually sent ?

[Sergey Ulanov, 2016/09/16 00:02:47]

I was planning to do that, but haven't actually implemented it yet (it's not
straightforward to do it cleanly and safely as there are several layers between
the encoder and pacer).

+      const WebrtcVideoEncoder::EncodedFrame& encoded_frame,
+      const webrtc::EncodedImageCallback::Result& send_result) = 0;
+};
+
+}  // namespace protocol
+}  // namespace remoting
+
+#endif  // REMOTING_PROTOCOL_WEBRTC_CAPTURE_SCHEDULER_H_