Adding getParameters/setParameters APIs to RtpReceiver.

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
index 57c678032a19be0c489a9fad4a00895f9efdbd25..b91a20021532f555f29b1a66164d8463ac4112f0 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
@@ -17,6 +17,7 @@
 #import "RTCMediaConstraints+Private.h"
 #import "RTCMediaStream+Private.h"
 #import "RTCPeerConnectionFactory+Private.h"
+#import "RTCRtpReceiver+Private.h"
 #import "RTCRtpSender+Private.h"
 #import "RTCSessionDescription+Private.h"
 #import "RTCStatsReport+Private.h"
@@ -342,6 +343,18 @@ void PeerConnectionDelegateAdapter::OnIceCandidate(
   return senders;
 }
 
+- (NSArray<RTCRtpReceiver *> *)receivers {
+  std::vector<rtc::scoped_refptr<webrtc::RtpReceiverInterface>> nativeReceivers(
+      _peerConnection->GetReceivers());
+  NSMutableArray *receivers = [[NSMutableArray alloc] init];
+  for (const auto &nativeReceiver : nativeReceivers) {
+    RTCRtpReceiver *receiver =
+        [[RTCRtpReceiver alloc] initWithNativeRtpReceiver:nativeReceiver];
+    [receivers addObject:receiver];
+  }
+  return receivers;
+}
+
 #pragma mark - Private
 
 + (webrtc::PeerConnectionInterface::SignalingState)nativeSignalingStateForState: