create a separate WebMediaPlayer for URL derived from media stream

webkit/media/video_frame_provider.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 WEBKIT_MEDIA_VIDEO_FRAME_PROVIDER_H_
+#define WEBKIT_MEDIA_VIDEO_FRAME_PROVIDER_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+
+namespace media {
+class VideoFrame;
+}
+
+namespace webkit_media {
+
+typedef base::Callback<void(const scoped_refptr<media::VideoFrame>&)> RepaintCB;

[scherkus (not reviewing), 2012/09/07 11:44:03]

move this inside VFP class

[wjia(left Chromium), 2012/09/13 01:22:07]

Done.

+
+// Define an interface to provide a sequence of video frames to clients.
+class VideoFrameProvider
+    : public base::RefCountedThreadSafe<VideoFrameProvider> {

[scherkus (not reviewing), 2012/09/07 11:44:03]

does this have to be refcounted?

would having implementors use weak pointers suffice?

[wjia(left Chromium), 2012/09/13 01:22:07]

Some derived class needs ref counted, because it will be essentially accessed on
at least 2 threads. For example, LocalVideoCapture is accessed on both main
thread and VideoCaptureImpl's working thread. For LocalVideoCapture, it's a bit
complicated since a Proxy is used. But the proxy is scoped_ptr'ed by
LocalVideoCapture. That means LocalVideoCapture can't go away before its user
confirms LocalVideoCapture will not be used any longer.

[scherkus (not reviewing), 2012/09/13 10:25:24]

Being accessed on two threads doesn't imply a class needs to be refcounted.

See my other comments in WMPMS about this. It seems you really want a way for
LVC to tell VC to not call itself anymore OR move the use-after-free handling
inside of VideoCaptureHandlerProxy but not LVC.

[wjia(left Chromium), 2012/09/19 03:22:06]

You are right. I have thought about refactoring
media::VideoCapture::EventHandler to support weak ptr. When one EventHandler
registers with VideoCaptureImpl, it also provides a MessageLoopProxy on which
the EventHandler will be destructed. When sending an event to the EventHandler,
VideoCaptureImpl will always post a task to that MLP. This can guarantee that
EventHandler can be deleted any time without a use-after-free case.

+ public:
+  virtual void Start() = 0;

[scherkus (not reviewing), 2012/09/07 11:44:03]

docs for interface methods

[wjia(left Chromium), 2012/09/13 01:22:07]

Done.

+  virtual void Stop() = 0;
+  virtual void Play() = 0;
+  virtual void Pause() = 0;
+
+ protected:
+  friend class base::RefCountedThreadSafe<VideoFrameProvider>;
+  VideoFrameProvider();
+  virtual ~VideoFrameProvider();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(VideoFrameProvider);
+};
+
+}  // namespace webkit_media
+
+#endif  // WEBKIT_MEDIA_VIDEO_FRAME_PROVIDER_H_