Update WebrtcFrameScheduler to avoid concurrent captures.

remoting/protocol/webrtc_dummy_video_encoder.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_DUMMY_VIDEO_ENCODER_H_
 #define REMOTING_PROTOCOL_WEBRTC_DUMMY_VIDEO_ENCODER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 70 matching lines @@
       const override;
   bool EncoderTypeHasInternalSource(webrtc::VideoCodecType type) const override;
   void DestroyVideoEncoder(webrtc::VideoEncoder* encoder) override;
 
   webrtc::EncodedImageCallback::Result SendEncodedFrame(
       const WebrtcVideoEncoder::EncodedFrame& packet,
       base::TimeTicks capture_time);
 
   void SetVideoChannelStateObserver(
       base::WeakPtr<VideoChannelStateObserver> video_channel_state_observer);
+  base::WeakPtr<VideoChannelStateObserver>
+  get_video_channel_state_observer_for_tests() {
+    return video_channel_state_observer_;
+  }
 
  private:
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
 
   std::vector<cricket::WebRtcVideoEncoderFactory::VideoCodec> codecs_;
 
   // Protects |video_channel_state_observer_| and |encoders_|.
   base::Lock lock_;
   base::WeakPtr<VideoChannelStateObserver> video_channel_state_observer_;
   std::vector<std::unique_ptr<WebrtcDummyVideoEncoder>> encoders_;
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_WEBRTC_DUMMY_VIDEO_ENCODER_H_