Fix WebrtcVideoStream to handle failed capture requests.

remoting/codec/webrtc_video_encoder_vpx.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_CODEC_WEBRTC_VIDEO_ENCODER_VPX_H_
 #define REMOTING_CODEC_WEBRTC_VIDEO_ENCODER_VPX_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
@@ skipping 23 matching lines @@
   static std::unique_ptr<WebrtcVideoEncoderVpx> CreateForVP9();
 
   ~WebrtcVideoEncoderVpx() override;
 
   void SetTickClockForTests(base::TickClock* tick_clock);
 
   void SetLosslessEncode(bool want_lossless);
   void SetLosslessColor(bool want_lossless);
 
   // WebrtcVideoEncoder interface.
-  std::unique_ptr<EncodedFrame> Encode(const webrtc::DesktopFrame& frame,
+  std::unique_ptr<EncodedFrame> Encode(const webrtc::DesktopFrame* frame,
                                        const FrameParams& params) override;
 
  private:
   explicit WebrtcVideoEncoderVpx(bool use_vp9);
 
   // (Re)Configures this instance to encode frames of the specified |size|,
   // with the configured lossless color & encoding modes.
   void Configure(const webrtc::DesktopSize& size);
 
   // Updates codec configuration.
   void UpdateConfig(const FrameParams& params);
 
   // Prepares |image_| for encoding. Writes updated rectangles into
   // |updated_region|.
-  void PrepareImage(const webrtc::DesktopFrame& frame,
+  void PrepareImage(const webrtc::DesktopFrame* frame,
                     webrtc::DesktopRegion* updated_region);
 
   // Clears active map.
   void ClearActiveMap();
 
   // Updates the active map according to |updated_region|. Active map is then
   // given to the encoder to speed up encoding.
   void SetActiveMapFromRegion(const webrtc::DesktopRegion& updated_region);
 
   // Adds areas changed in the most recent frame to |updated_region|. This
@@ skipping 26 matching lines @@
 
   base::DefaultTickClock default_tick_clock_;
   base::TickClock* clock_;
 
   DISALLOW_COPY_AND_ASSIGN(WebrtcVideoEncoderVpx);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CODEC_WEBRTC_VIDEO_ENCODER_VPX_H_