Remove event_channel() and control_channel() from Session interface.

remoting/protocol/protobuf_video_writer.cc

Index: remoting/protocol/protobuf_video_writer.cc
diff --git a/remoting/protocol/protobuf_video_writer.cc b/remoting/protocol/protobuf_video_writer.cc
index 10e1e53b5d3be8248c7309dea7557187becebc15..9b15a79ea21384a6d125656e9f7c4664a06be923 100644
--- a/remoting/protocol/protobuf_video_writer.cc
+++ b/remoting/protocol/protobuf_video_writer.cc
@@ -57,6 +57,10 @@ void ProtobufVideoWriter::Close() {
   }
 }
 
+bool ProtobufVideoWriter::is_connected() {
+  return channel_.get() != NULL;
+}
+
 void ProtobufVideoWriter::ProcessVideoPacket(const VideoPacket* packet,
                                              const base::Closure& done) {
   buffered_writer_->Write(SerializeAndFrameMessage(*packet), done);