Add LookupDtlsTransportByMid to proxy map

Bug: chromium:907849
Change-Id: Ib707f18fdf67617967b83cd17f0454d182b8011f
Reviewed-on: https://webrtc-review.googlesource.com/c/112907
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25885}

api/peerconnectioninterface.cc

@@ -178,6 +178,7 @@ bool PeerConnectionInterface::StartRtcEventLog(
 
 rtc::scoped_refptr<DtlsTransportInterface>
 PeerConnectionInterface::LookupDtlsTransportByMid(const std::string& mid) {
+  RTC_NOTREACHED();
   return nullptr;
 }
 

api/peerconnectioninterface.h

@@ -1034,9 +1034,9 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
   // In the Javascript API, DtlsTransport is a property of a sender, but
   // because the PeerConnection owns the DtlsTransport in this implementation,
   // it is better to look them up on the PeerConnection.
+  // TODO(hta): Remove default implementation after updating Chrome.
   virtual rtc::scoped_refptr<DtlsTransportInterface> LookupDtlsTransportByMid(
       const std::string& mid);
-  // TODO(hta): Remove default implementation.
 
   // Returns the current SignalingState.
   virtual SignalingState signaling_state() = 0;

api/peerconnectionproxy.h

@@ -119,6 +119,9 @@ PROXY_METHOD1(bool,
               const std::vector<cricket::Candidate>&);
 PROXY_METHOD1(void, SetAudioPlayout, bool)
 PROXY_METHOD1(void, SetAudioRecording, bool)
+PROXY_METHOD1(rtc::scoped_refptr<DtlsTransportInterface>,
+              LookupDtlsTransportByMid,
+              const std::string&)
 PROXY_METHOD1(RTCError, SetBitrate, const BitrateSettings&);
 PROXY_METHOD1(void,
               SetBitrateAllocationStrategy,

pc/test/fakepeerconnectionbase.h

@@ -189,6 +189,11 @@ class FakePeerConnectionBase : public PeerConnectionInternal {
 
   void SetAudioRecording(bool recording) override {}
 
+  rtc::scoped_refptr<DtlsTransportInterface> LookupDtlsTransportByMid(
+      const std::string& mid) {
+    return nullptr;
+  }
+
   SignalingState signaling_state() override { return SignalingState::kStable; }
 
   IceConnectionState ice_connection_state() override {