Deliver video frames on libjingle worker thread to WebRtcVideoCapturerAdapter.

content/renderer/media/webrtc/webrtc_video_capturer_adapter.h

 // Copyright 2014 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 CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_VIDEO_CAPTURER_ADAPTER_H_
 #define CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_VIDEO_CAPTURER_ADAPTER_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/threading/thread_checker.h"
 #include "content/common/content_export.h"
 #include "media/base/video_frame.h"
 #include "media/video/capture/video_capture_types.h"
 #include "third_party/libjingle/source/talk/media/base/videocapturer.h"
 
 namespace content {
 
 // WebRtcVideoCapturerAdapter implements a simple cricket::VideoCapturer that is
 // used for VideoCapturing in libJingle and especially in PeerConnections.
 // The class is created and destroyed on the main render thread.
 // PeerConnection access cricket::VideoCapturer from a libJingle worker thread.
+// An instance of WebRtcVideoCapturerAdapter is owned by an instance of
+// webrtc::VideoSourceInterface in libJingle. The implementation of
+// webrtc::VideoSourceInterface guarantees that this object is not deleted
+// while it is still used in libJingle.
 class CONTENT_EXPORT WebRtcVideoCapturerAdapter
     : NON_EXPORTED_BASE(public cricket::VideoCapturer) {
  public:
   explicit WebRtcVideoCapturerAdapter(bool is_screencast);
   virtual ~WebRtcVideoCapturerAdapter();
 
+  // OnFrameCaptured delivers video frames to libjingle. It must be called on
+  // libjingles worker thread.
   // This method is virtual for testing purposes.
   virtual void OnFrameCaptured(const scoped_refptr<media::VideoFrame>& frame);
 
  private:
   // cricket::VideoCapturer implementation.
   // These methods are accessed from a libJingle worker thread.
   virtual cricket::CaptureState Start(
       const cricket::VideoFormat& capture_format) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual bool IsRunning() OVERRIDE;
   virtual bool GetPreferredFourccs(std::vector<uint32>* fourccs) OVERRIDE;
   virtual bool GetBestCaptureFormat(const cricket::VideoFormat& desired,
                                     cricket::VideoFormat* best_format) OVERRIDE;
   virtual bool IsScreencast() const OVERRIDE;
 
   void UpdateI420Buffer(const scoped_refptr<media::VideoFrame>& src);
 
- private:
+  // |thread_checker_| is bound to the libjingle worker thread.
+  base::ThreadChecker thread_checker_;
+
   const bool is_screencast_;
   bool running_;
   base::TimeDelta first_frame_timestamp_;
   // |buffer_| used if cropping is needed. It is created only if needed and
   // owned by WebRtcVideoCapturerAdapter. If its created, it exists until
   // WebRtcVideoCapturerAdapter is destroyed.
   uint8* buffer_;
   size_t buffer_size_;
   scoped_ptr<cricket::CapturedFrame> captured_frame_;
 
   DISALLOW_COPY_AND_ASSIGN(WebRtcVideoCapturerAdapter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_VIDEO_CAPTURER_ADAPTER_H_