Delete unused sigslot variables.

- Usage of these sigslots are removed in previous changes in WebRTC
  and downstream repositories.
- Remove one more usage of the variables in port_unnittests.

No-Try: True
Bug: webrtc:11943
Change-Id: Ia424f598248a5d9a0cf88f041641a3dd8aa6effe
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206500
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33205}

p2p/base/dtls_transport.cc

@@ -820,8 +820,6 @@ void DtlsTransport::set_dtls_state(DtlsTransportState state) {
 }
 
 void DtlsTransport::OnDtlsHandshakeError(rtc::SSLHandshakeError error) {
-  // Keep the old signaling for downstream usage.
-  SignalDtlsHandshakeError(error);
   SendDtlsHandshakeError(error);
 }
 

p2p/base/dtls_transport_internal.h

@@ -117,7 +117,6 @@ class DtlsTransportInternal : public rtc::PacketTransportInternal {
   sigslot::signal2<DtlsTransportInternal*, DtlsTransportState> SignalDtlsState;
 
   // Emitted whenever the Dtls handshake failed on some transport channel.
-  sigslot::signal1<rtc::SSLHandshakeError> SignalDtlsHandshakeError;
   // F: void(rtc::SSLHandshakeError)
   template <typename F>
   void SubscribeDtlsHandshakeError(F&& callback) {

p2p/base/port.cc

@@ -921,7 +921,6 @@ void Port::OnConnectionDestroyed(Connection* conn) {
 void Port::Destroy() {
   RTC_DCHECK(connections_.empty());
   RTC_LOG(LS_INFO) << ToString() << ": Port deleted";
-  SignalDestroyed(this);
   SendPortDestroyed(this);
   delete this;
 }

p2p/base/port_interface.h

@@ -114,7 +114,6 @@ class PortInterface {
 
   // Signaled when this port decides to delete itself because it no longer has
   // any usefulness.
-  sigslot::signal1<PortInterface*> SignalDestroyed;
   virtual void SubscribePortDestroyed(
       std::function<void(PortInterface*)> callback) = 0;
 

p2p/base/port_unittest.cc

@@ -778,7 +778,8 @@ class PortTest : public ::testing::Test, public sigslot::has_slots<> {
   bool role_conflict() const { return role_conflict_; }
 
   void ConnectToSignalDestroyed(PortInterface* port) {
-    port->SignalDestroyed.connect(this, &PortTest::OnDestroyed);
+    port->SubscribePortDestroyed(
+        [this](PortInterface* port) { OnDestroyed(port); });
   }
 
   void OnDestroyed(PortInterface* port) { ++ports_destroyed_; }