Refactor video capturing code in the render process

media/video/capture/video_capture_proxy.h

-// Copyright (c) 2012 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 MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_PROXY_H_
-#define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_PROXY_H_
-
-#include "base/compiler_specific.h"
-#include "base/memory/ref_counted.h"
-#include "media/video/capture/video_capture.h"
-
-namespace base {
-class SingleThreadTaskRunner;
-}
-
-namespace media {
-
-// This is a helper class to proxy a VideoCapture::EventHandler. In the renderer
-// process, the VideoCaptureImpl calls its handler on a "Video Capture" thread,
-// this class allows seamless proxying to another thread ("main thread"), which
-// would be the thread where the instance of this class is created. The
-// "proxied" handler is then called on that thread.
-// Since the VideoCapture is living on the "Video Capture" thread, querying its
-// state from the "main thread" is fundamentally racy. Instead this class keeps
-// track of the state every time it is called by the VideoCapture (on the VC
-// thread), and forwards that information to the main thread.
-class MEDIA_EXPORT VideoCaptureHandlerProxy
-    : public VideoCapture::EventHandler {
- public:
-  struct VideoCaptureState {
-    VideoCaptureState() : started(false), frame_rate(0) {}
-    bool started;
-    int frame_rate;
-  };
-
-  // Called on main thread.
-  VideoCaptureHandlerProxy(
-      VideoCapture::EventHandler* proxied,
-      const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner);
-  virtual ~VideoCaptureHandlerProxy();
-
-  // Retrieves the state of the VideoCapture. Must be called on main thread.
-  const VideoCaptureState& state() const { return state_; }
-
-  // VideoCapture::EventHandler implementation, called on VC thread.
-  virtual void OnStarted(VideoCapture* capture) OVERRIDE;
-  virtual void OnStopped(VideoCapture* capture) OVERRIDE;
-  virtual void OnPaused(VideoCapture* capture) OVERRIDE;
-  virtual void OnError(VideoCapture* capture, int error_code) OVERRIDE;
-  virtual void OnRemoved(VideoCapture* capture) OVERRIDE;
-  virtual void OnFrameReady(VideoCapture* capture,
-                            const scoped_refptr<VideoFrame>& frame) OVERRIDE;
-
- private:
-  // Called on main thread.
-  void OnStartedOnMainThread(
-      VideoCapture* capture,
-      const VideoCaptureState& state);
-  void OnStoppedOnMainThread(
-      VideoCapture* capture,
-      const VideoCaptureState& state);
-  void OnPausedOnMainThread(
-      VideoCapture* capture,
-      const VideoCaptureState& state);
-  void OnErrorOnMainThread(
-      VideoCapture* capture,
-      const VideoCaptureState& state,
-      int error_code);
-  void OnRemovedOnMainThread(
-      VideoCapture* capture,
-      const VideoCaptureState& state);
-  void OnFrameReadyOnMainThread(VideoCapture* capture,
-                                const VideoCaptureState& state,
-                                const scoped_refptr<VideoFrame>& frame);
-
-  // Only accessed from main thread.
-  VideoCapture::EventHandler* proxied_;
-  VideoCaptureState state_;
-
-  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
-};
-
-}  // namespace media
-
-#endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_PROXY_H_