Add CancelChannelCreation() in protocol::Session interface.

remoting/protocol/rtp_video_writer.cc

Index: remoting/protocol/rtp_video_writer.cc
diff --git a/remoting/protocol/rtp_video_writer.cc b/remoting/protocol/rtp_video_writer.cc
index c188d660daaa799388b1bccd4b1f666b8730f6b1..dce34fc09635bb6d6a226770eeb4828bb12a77d7 100644
--- a/remoting/protocol/rtp_video_writer.cc
+++ b/remoting/protocol/rtp_video_writer.cc
@@ -21,7 +21,8 @@ const int kMtu = 1200;
 }  // namespace
 
 RtpVideoWriter::RtpVideoWriter(base::MessageLoopProxy* message_loop)
-    : initialized_(false),
+    : session_(NULL),
+      initialized_(false),
       rtp_writer_(message_loop) {
 }
 
@@ -31,6 +32,7 @@ RtpVideoWriter::~RtpVideoWriter() {
 
 void RtpVideoWriter::Init(protocol::Session* session,
                           const InitializedCallback& callback) {
+  session_ = session;
   initialized_callback_ = callback;
   session->CreateDatagramChannel(
       kVideoRtpChannelName,
@@ -72,6 +74,11 @@ void RtpVideoWriter::Close() {
   rtp_writer_.Close();
   rtp_channel_.reset();
   rtcp_channel_.reset();
+  if (session_) {
+    session_->CancelChannelCreation(kVideoRtpChannelName);
+    session_->CancelChannelCreation(kVideoRtcpChannelName);
+    session_ = NULL;
+  }
 }
 
 void RtpVideoWriter::ProcessVideoPacket(const VideoPacket* packet,