Remove legacy SetTargetTransferRateObserver

Bug: webrtc:9719
Change-Id: I04e892ce0f2af5c48040dd92ff0701209104fe65
Reviewed-on: https://webrtc-review.googlesource.com/c/111287
Reviewed-by: Anton Sukhanov <sukhanov@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25734}
diff --git a/api/media_transport_interface.cc b/api/media_transport_interface.cc
index 039a4a1..ef223aa 100644
--- a/api/media_transport_interface.cc
+++ b/api/media_transport_interface.cc
@@ -114,9 +114,6 @@
 void MediaTransportInterface::RemoveTargetTransferRateObserver(
     webrtc::TargetTransferRateObserver* observer) {}
 
-void MediaTransportInterface::SetTargetTransferRateObserver(
-    webrtc::TargetTransferRateObserver* observer) {}
-
 void MediaTransportInterface::AddTargetTransferRateObserver(
     webrtc::TargetTransferRateObserver* observer) {}
 
diff --git a/api/media_transport_interface.h b/api/media_transport_interface.h
index 5aac712..b10dd63 100644
--- a/api/media_transport_interface.h
+++ b/api/media_transport_interface.h
@@ -335,15 +335,6 @@
   // pass a nullptr.
   virtual void SetReceiveVideoSink(MediaTransportVideoSinkInterface* sink) = 0;
 
-  // Sets a target bitrate observer. Before media transport is destructed
-  // the observer must be unregistered (set to nullptr).
-  // A newly registered observer will be called back with the latest recorded
-  // target rate, if available.
-  // TODO(psla): This method will be removed, in favor of
-  // AddTargetTransferRateObserver.
-  virtual void SetTargetTransferRateObserver(
-      TargetTransferRateObserver* observer);
-
   // Adds a target bitrate observer. Before media transport is destructed
   // the observer must be unregistered (by calling
   // RemoveTargetTransferRateObserver).
diff --git a/api/test/fake_media_transport.h b/api/test/fake_media_transport.h
index 8018529..eb6ec93 100644
--- a/api/test/fake_media_transport.h
+++ b/api/test/fake_media_transport.h
@@ -55,9 +55,6 @@
     return settings_.pre_shared_key;
   }
 
-  void SetTargetTransferRateObserver(
-      webrtc::TargetTransferRateObserver* observer) override {}
-
   RTCError SendData(int channel_id,
                     const SendDataParams& params,
                     const rtc::CopyOnWriteBuffer& buffer) override {
diff --git a/api/test/loopback_media_transport.h b/api/test/loopback_media_transport.h
index dbb674d..48255b1 100644
--- a/api/test/loopback_media_transport.h
+++ b/api/test/loopback_media_transport.h
@@ -52,11 +52,6 @@
     wrapped_->SetReceiveVideoSink(sink);
   }
 
-  void SetTargetTransferRateObserver(
-      webrtc::TargetTransferRateObserver* observer) override {
-    wrapped_->SetTargetTransferRateObserver(observer);
-  }
-
   void SetMediaTransportStateCallback(
       MediaTransportStateCallback* callback) override {
     wrapped_->SetMediaTransportStateCallback(callback);
@@ -178,9 +173,6 @@
 
     void SetReceiveVideoSink(MediaTransportVideoSinkInterface* sink) override {}
 
-    void SetTargetTransferRateObserver(
-        webrtc::TargetTransferRateObserver* observer) override {}
-
     void SetMediaTransportStateCallback(
         MediaTransportStateCallback* callback) override {
       rtc::CritScope lock(&sink_lock_);