Adding getParameters/setParameters APIs to RtpReceiver.

webrtc/sdk/objc/Framework/Classes/RTCRtpSender+Private.h

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #import "WebRTC/RTCRtpSender.h"
 
 #include "webrtc/api/rtpsenderinterface.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface RTCRtpSender ()
 
+@property(nonatomic, readonly)
+    rtc::scoped_refptr<webrtc::RtpSenderInterface> nativeRtpSender;
+
 /** Initialize an RTCRtpSender with a native RtpSenderInterface. */
 - (instancetype)initWithNativeRtpSender:
     (rtc::scoped_refptr<webrtc::RtpSenderInterface>)nativeRtpSender
     NS_DESIGNATED_INITIALIZER;
 
 @end
 
 NS_ASSUME_NONNULL_END