[PPAPI] Implement media stream video track API

content/renderer/pepper/pepper_media_stream_track_host_base.h

+// Copyright (c) 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_PEPPER_PEPPER_MEDIA_STREAM_TRACK_HOST_BASE_H_
+#define CONTENT_RENDERER_PEPPER_PEPPER_MEDIA_STREAM_TRACK_HOST_BASE_H_
+
+#include "base/compiler_specific.h"
+#include "content/common/content_export.h"
+#include "ppapi/host/resource_host.h"
+#include "ppapi/shared_impl/media_stream_frame_buffer.h"
+
+namespace content {
+
+class RendererPpapiHost;
+
+class PepperMediaStreamTrackHostBase
+    : public ppapi::host::ResourceHost,
+      public ppapi::MediaStreamFrameBuffer::Delegate {
+ protected:
+  PepperMediaStreamTrackHostBase(RendererPpapiHost* host,
+                                 PP_Instance instance,
+                                 PP_Resource resource);
+
+  virtual ~PepperMediaStreamTrackHostBase();
+
+  bool InitFrames(int32_t number_of_frames, int32_t frame_size);
+
+  virtual int32_t OnResourceMessageReceived(
+      const IPC::Message& msg,
+      ppapi::host::HostMessageContext* context) OVERRIDE;
+
+  ppapi::MediaStreamFrameBuffer* frame_buffer() { return &frame_buffer_; }
+
+  // Enqueue a frame into plugin's |frame_buffer_|.

[dmichael (off chromium), 2014/01/09 21:06:47]

Can you clear up what this actually means? Does it mean that the host should
call this when aframe is ready to pass to the plugin for reading?

[Peng, 2014/01/10 19:14:30]

When a frame is ready, the host will call this function to send the frame index
to the plugin, and then the plugin will add the index into a queue for reading.

And I would like use this base class both for video input and output. For video
input host, when a frame is consumed by host (rendered to <video> element), host
will call this function to send the consumed frame index to the plugin, and then
the plugin can reuse the frame for new frames.

I think this function's name is not very good. Do you have any suggestion?

+  void PluginEnqueueFrame(int32_t index);
+
+  // Subclass should implement this method to get notification when the track is
+  // being closed.
+  virtual void OnClose() = 0;
+
+  // Messages handlers:
+  int32_t OnHostMsgEnqueueFrame(ppapi::host::HostMessageContext* context,
+                                int32_t index);
+  int32_t OnHostMsgClose(ppapi::host::HostMessageContext* context);
+
+ private:
+  RendererPpapiHost* host_;
+
+  ppapi::MediaStreamFrameBuffer frame_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(PepperMediaStreamTrackHostBase);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_PEPPER_PEPPER_MEDIA_STREAM_TRACK_HOST_BASE_H_