Basic use implementation for MediaStream from Canvas: captureStream()

content/renderer/media/canvas_capture_handler.h

+// Copyright 2015 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_CANVAS_CAPTURE_HANDLER_H_
+#define CONTENT_RENDERER_MEDIA_CANVAS_CAPTURE_HANDLER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_checker.h"
+#include "content/common/content_export.h"
+#include "media/base/video_capturer_source.h"
+#include "media/base/video_frame_pool.h"
+#include "media/base/video_types.h"
+#include "third_party/WebKit/public/platform/WebCanvasCaptureHandler.h"
+#include "third_party/WebKit/public/platform/WebMediaStream.h"
+#include "third_party/WebKit/public/platform/WebSize.h"
+#include "third_party/WebKit/public/platform/WebSkImage.h"
+#include "third_party/skia/include/core/SkImage.h"
+
+namespace content {
+
+class CONTENT_EXPORT CanvasCaptureHandler final
+    : public NON_EXPORTED_BASE(blink::WebCanvasCaptureHandler),
+      public base::RefCounted<CanvasCaptureHandler> {

[perkj_chrome, 2015/11/26 18:52:14]

RefCounted? Does this object really need to be? It seems like the only place
that holds a reference to this object is
CanvasCaptureHandler::VideoCapturerSource that is directly owned by a blink
object. 

[emircan, 2015/12/01 00:25:45]

Here is my logic. I am not sure if I am doing the right thing, but I am
following CastReceiverSession::VideoCapturerSource design here.

::VideoCapturerSource is owned by MediaStreamSource in blink side.
CanvasCaptureHandler is owned by CanvasDrawListener which is owned by
CanvasCaptureMediaStream in blink side. 

I want to forward the calls to ::VideoCapturerSource to CanvasCaptureHandler so
I need a reference between. My assumption is that CanvasCaptureHandler is alive
during the lifetime of ::VideoCapturerSource because the MediaStreamSource goes
out of scope before CanvasCaptureMediaStream does. 

I am trying to have a reference to CanvasCaptureHandler from 2 classes:
CanvasDrawListener on blink side, and ::VideoCapturerSource from Chrome side.
AFAIU, CanvasDrawListener needs to own ptr it receives. ::VideoCapturerSource
cannot have a scoped_ptr<> and a naked pointer didn't look right to me. However,
thinking again, it needs to be a naked ptr as I do not want to call
CanvasCaptureHandler dtor() from Chrome side. So, I am changing it. 

[0]
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/renderer/me...

+ public:
+  CanvasCaptureHandler(const blink::WebSize& size,
+                       blink::WebMediaStream* stream);
+
+  // blink::WebCanvasCaptureHandler Implementation.
+  void sendNewFrame(const blink::WebSkImage& image) override;
+  bool needsNewFrameCapture() const override;
+
+  // media::VideoCapturerSource Implementation.

[perkj_chrome, 2015/11/26 18:52:14]

This class does not implement media::VideoCapturerSource .

[emircan, 2015/12/01 00:25:45]

Leftover from earlier. Fixing it. 

+  void StartVideoCapture(
+      const media::VideoCaptureParams& params,
+      const media::VideoCapturerSource::VideoCaptureDeliverFrameCB&
+          new_frame_callback,
+      const media::VideoCapturerSource::RunningCallback& running_callback);
+  void StopVideoCapture();
+  blink::WebSize GetSourceSize() { return size_; }
+
+ private:
+  friend class base::RefCounted<CanvasCaptureHandler>;
+  virtual ~CanvasCaptureHandler();
+
+  class VideoCapturerSource;
+  // An object that does all the work of running |new_frame_callback_|.
+  // Destroyed on |io_task_runner_| after the class is destroyed.
+  class CanvasCaptureHandlerDelegate;
+  scoped_ptr<CanvasCaptureHandlerDelegate> delegate_;
+  void createNewFrame(const blink::WebSkImage& image);
+
+  media::VideoCaptureFormat capture_format_;
+  bool ask_for_new_frame_;
+
+  const blink::WebSize size_;
+  gfx::Size last_size;
+  std::vector<uint8> temp_data_;
+  size_t row_bytes_;
+  SkImageInfo image_info_;
+  media::VideoFramePool frame_pool_;
+
+  const scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+  // Bound to the main render thread.
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(CanvasCaptureHandler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_CANVAS_CAPTURE_HANDLER_H_