Remove video_channel() from Session interface

remoting/protocol/video_writer.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
 // VideoWriter is a generic interface for a video stream writer. RtpVideoWriter
 // and ProtobufVideoWriter implement this interface for RTP and protobuf video
 // streams. VideoWriter is used by ConnectionToClient to write into the video
 // stream.
 
 #ifndef REMOTING_PROTOCOL_VIDEO_WRITER_H_
 #define REMOTING_PROTOCOL_VIDEO_WRITER_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "remoting/protocol/video_stub.h"
 
 namespace remoting {
 namespace protocol {
 
 class Session;
 class SessionConfig;
 
 class VideoWriter : public VideoStub {
  public:
   virtual ~VideoWriter();
 
+  // The callback is called when initialization is finished. The
+  // parameter is set to true on success.
+  typedef base::Callback<void(bool)> InitializedCallback;
+
   static VideoWriter* Create(const SessionConfig* config);
 
   // Initializes the writer.
-  virtual void Init(Session* session) = 0;
+  virtual void Init(Session* session, const InitializedCallback& callback) = 0;
 
   // Stops writing. Must be called on the network thread before this
   // object is destroyed.
   virtual void Close() = 0;
 
  protected:
   VideoWriter() { }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoWriter);
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_VIDEO_WRITER_H_