Remove sigslot dependency from RtpTransceiver

Bug: webrtc:11943
Change-Id: I4212c90088671150f4fe828ad238380bf71b938e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/295720
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Auto-Submit: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39440}
diff --git a/pc/rtp_transceiver.h b/pc/rtp_transceiver.h
index 0844b34..530522a 100644
--- a/pc/rtp_transceiver.h
+++ b/pc/rtp_transceiver.h
@@ -43,7 +43,6 @@
 #include "pc/rtp_sender_proxy.h"
 #include "pc/rtp_transport_internal.h"
 #include "pc/session_description.h"
-#include "rtc_base/third_party/sigslot/sigslot.h"
 #include "rtc_base/thread_annotations.h"
 
 namespace cricket {
@@ -82,8 +81,7 @@
 // MediaType specified in the constructor. Audio RtpTransceivers will have
 // AudioRtpSenders, AudioRtpReceivers, and a VoiceChannel. Video RtpTransceivers
 // will have VideoRtpSenders, VideoRtpReceivers, and a VideoChannel.
-class RtpTransceiver : public RtpTransceiverInterface,
-                       public sigslot::has_slots<> {
+class RtpTransceiver : public RtpTransceiverInterface {
  public:
   // Construct a Plan B-style RtpTransceiver with no senders, receivers, or
   // channel set.
@@ -257,10 +255,6 @@
   // the webrtc-pc specification, described under the stop() method.
   void StopTransceiverProcedure();
 
-  // Fired when the RtpTransceiver state changes such that negotiation is now
-  // needed (e.g., in response to a direction change).
-  //  sigslot::signal0<> SignalNegotiationNeeded;
-
   // RtpTransceiverInterface implementation.
   cricket::MediaType media_type() const override;
   absl::optional<std::string> mid() const override;