[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 {

[bbudge, 2014/01/14 17:13:52]

I can't find any override of the Delegate::OnNewFrameEnqueued method on this
class or on the subclass. Is there a follow-up patch that will define that?

[Peng, 2014/01/14 17:26:10]

Yes. I plan to use this class as a base class for both A/V input and output.
For A/V output(the 'output' is from plugin's point of view), subclasses will
implement OnNewFrameEnqueued() to deliver frames to blink::MediaStreamTrack for
rendering, etc.

+ protected:
+  PepperMediaStreamTrackHostBase(RendererPpapiHost* host,
+                                 PP_Instance instance,
+                                 PP_Resource resource);
+  virtual ~PepperMediaStreamTrackHostBase();
+
+  bool InitFrames(int32_t number_of_frames, int32_t frame_size);
+
+  ppapi::MediaStreamFrameBuffer* frame_buffer() { return &frame_buffer_; }
+
+  // Sends a frame index to the corresponding MediaStreamTrackResourceBase
+  // via an IPC message. The resource adds the frame index into its
+  // |frame_buffer_| for reading or writing. Also see |MediaStreamFrameBuffer|.
+  void SendEnqueueFrameMessageToPlugin(int32_t index);
+
+ private:
+  // Subclasses must implement this method to clean up when the track is closed.
+  virtual void OnClose() = 0;
+
+  // ResourceMessageHandler overrides:
+  virtual int32_t OnResourceMessageReceived(
+      const IPC::Message& msg,
+      ppapi::host::HostMessageContext* context) OVERRIDE;
+
+  // Message handlers:
+  int32_t OnHostMsgEnqueueFrame(ppapi::host::HostMessageContext* context,
+                                int32_t index);
+  int32_t OnHostMsgClose(ppapi::host::HostMessageContext* context);
+
+  RendererPpapiHost* host_;
+
+  ppapi::MediaStreamFrameBuffer frame_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(PepperMediaStreamTrackHostBase);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_PEPPER_PEPPER_MEDIA_STREAM_TRACK_HOST_BASE_H_