Make BaseChannel::rtp_transport_ a unique_ptr.

webrtc/pc/channel.h

Index: webrtc/pc/channel.h
diff --git a/webrtc/pc/channel.h b/webrtc/pc/channel.h
index 8b3be2c14ea9e93a086ade1e9abab159a0b5be5f..ae3a29a2ffb1de42f48340f57a264cb3292e0906 100644
--- a/webrtc/pc/channel.h
+++ b/webrtc/pc/channel.h
@@ -397,7 +397,7 @@ class BaseChannel
   // If non-null, "X_dtls_transport_" will always equal "X_packet_transport_".
   DtlsTransportInternal* rtp_dtls_transport_ = nullptr;
   DtlsTransportInternal* rtcp_dtls_transport_ = nullptr;
-  webrtc::RtpTransport rtp_transport_;
+  std::unique_ptr<webrtc::RtpTransport> rtp_transport_;
   std::vector<std::pair<rtc::Socket::Option, int> > socket_options_;
   std::vector<std::pair<rtc::Socket::Option, int> > rtcp_socket_options_;
   SrtpFilter srtp_filter_;