Use CallbackList for DtlsState in dtls_transport.

- This contains a CallbackList disconnect and handled it
  by taking the given subscription tag to subscribe and unsubscribe.
- Left the original sigslot variable until downstream is update after
  this change.

Bug: webrtc:11943
No-Try: True
Change-Id: Ie96d74b9594eae11beaa552f61e40f451242bfab
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/203780
Commit-Queue: Lahiru Ginnaliya Gamathige <glahiru@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33285}

p2p/base/dtls_transport.cc

@@ -817,6 +817,7 @@ void DtlsTransport::set_dtls_state(DtlsTransportState state) {
                       << " to " << state;
   dtls_state_ = state;
   SignalDtlsState(this, state);
+  SendDtlsState(this, state);
 }
 
 void DtlsTransport::OnDtlsHandshakeError(rtc::SSLHandshakeError error) {

p2p/base/dtls_transport_internal.h

@@ -115,6 +115,25 @@ class DtlsTransportInternal : public rtc::PacketTransportInternal {
   virtual IceTransportInternal* ice_transport() = 0;
 
   sigslot::signal2<DtlsTransportInternal*, DtlsTransportState> SignalDtlsState;
+  // F: void(DtlsTransportInternal*, const DtlsTransportState)
+  template <typename F>
+  void SubscribeDtlsState(F&& callback) {
+    dtls_state_callback_list_.AddReceiver(std::forward<F>(callback));
+  }
+
+  template <typename F>
+  void SubscribeDtlsState(const void* id, F&& callback) {
+    dtls_state_callback_list_.AddReceiver(id, std::forward<F>(callback));
+  }
+  // Unsubscribe the subscription with given id.
+  void UnsubscribeDtlsState(const void* id) {
+    dtls_state_callback_list_.RemoveReceivers(id);
+  }
+
+  void SendDtlsState(DtlsTransportInternal* transport,
+                     DtlsTransportState state) {
+    dtls_state_callback_list_.Send(transport, state);
+  }
 
   // Emitted whenever the Dtls handshake failed on some transport channel.
   // F: void(rtc::SSLHandshakeError)
@@ -134,6 +153,8 @@ class DtlsTransportInternal : public rtc::PacketTransportInternal {
   RTC_DISALLOW_COPY_AND_ASSIGN(DtlsTransportInternal);
   webrtc::CallbackList<const rtc::SSLHandshakeError>
       dtls_handshake_error_callback_list_;
+  webrtc::CallbackList<DtlsTransportInternal*, const DtlsTransportState>
+      dtls_state_callback_list_;
 };
 
 }  // namespace cricket

p2p/base/fake_dtls_transport.h

@@ -86,6 +86,7 @@ class FakeDtlsTransport : public DtlsTransportInternal {
   void SetDtlsState(DtlsTransportState state) {
     dtls_state_ = state;
     SignalDtlsState(this, dtls_state_);
+    SendDtlsState(this, dtls_state_);
   }
 
   // Simulates the two DTLS transports connecting to each other.

pc/dtls_srtp_transport.cc

@@ -277,14 +277,17 @@ void DtlsSrtpTransport::SetDtlsTransport(
   }
 
   if (*old_dtls_transport) {
-    (*old_dtls_transport)->SignalDtlsState.disconnect(this);
+    (*old_dtls_transport)->UnsubscribeDtlsState(this);
   }
 
   *old_dtls_transport = new_dtls_transport;
 
   if (new_dtls_transport) {
-    new_dtls_transport->SignalDtlsState.connect(
-        this, &DtlsSrtpTransport::OnDtlsState);
+    new_dtls_transport->SubscribeDtlsState(
+        this, [this](cricket::DtlsTransportInternal* transport,
+                     cricket::DtlsTransportState state) {
+          OnDtlsState(transport, state);
+        });
   }
 }
 

pc/dtls_transport.cc

@@ -51,8 +51,11 @@ DtlsTransport::DtlsTransport(
       ice_transport_(new rtc::RefCountedObject<IceTransportWithPointer>(
           internal_dtls_transport_->ice_transport())) {
   RTC_DCHECK(internal_dtls_transport_.get());
-  internal_dtls_transport_->SignalDtlsState.connect(
-      this, &DtlsTransport::OnInternalDtlsState);
+  internal_dtls_transport_->SubscribeDtlsState(
+      [this](cricket::DtlsTransportInternal* transport,
+             cricket::DtlsTransportState state) {
+        OnInternalDtlsState(transport, state);
+      });
   UpdateInformation();
 }
 

pc/sctp_transport.cc

@@ -94,8 +94,12 @@ void SctpTransport::SetDtlsTransport(
   if (internal_sctp_transport_) {
     if (transport) {
       internal_sctp_transport_->SetDtlsTransport(transport->internal());
-      transport->internal()->SignalDtlsState.connect(
-          this, &SctpTransport::OnDtlsStateChange);
+
+      transport->internal()->SubscribeDtlsState(
+          [this](cricket::DtlsTransportInternal* transport,
+                 cricket::DtlsTransportState state) {
+            OnDtlsStateChange(transport, state);
+          });
       if (info_.state() == SctpTransportState::kNew) {
         next_state = SctpTransportState::kConnecting;
       }