Added the API to create an RTCRtpSender to the Objective C wrapper.

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCRtpSender.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 <Foundation/Foundation.h>
 
 #import <WebRTC/RTCMacros.h>
 #import <WebRTC/RTCMediaStreamTrack.h>
 #import <WebRTC/RTCRtpParameters.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
 RTC_EXPORT
 @protocol RTCRtpSender <NSObject>
 
+/** A unique identifier for this sender. */
+@property(nonatomic, readonly) NSString *senderId;
+
 /** The currently active RTCRtpParameters, as defined in
  *  https://www.w3.org/TR/webrtc/#idl-def-RTCRtpParameters.
  */
-@property(nonatomic, readonly) RTCRtpParameters *parameters;
+@property(nonatomic) RTCRtpParameters *parameters;

[tkchin_webrtc, 2016/04/27 20:22:20]

nit: nonatomic, copy? 

[skvlad, 2016/04/27 23:00:58]

Good catch, copy is the right thing here.

 
 /** The RTCMediaStreamTrack associated with the sender.
  *  Note: reading this property returns a new instance of
  *  RTCMediaStreamTrack. Use isEqual: instead of == to compare
  *  RTCMediaStreamTrack instances.
  */
-@property(nonatomic, readonly) RTCMediaStreamTrack *track;
-
-/** Set the new RTCRtpParameters to be used by the sender.
- *  Returns YES if the new parameters were applied, NO otherwise.
- */
-- (BOOL)setParameters:(RTCRtpParameters *)parameters;
+@property(nonatomic) RTCMediaStreamTrack *track;

[tkchin_webrtc, 2016/04/27 20:22:20]

I'm surprised this wasn't throwing a warning - this seems to be nullable since
the impl returns nil sometimes.

nonatomic, copy, nullable

[skvlad, 2016/04/27 23:00:58]

Is "copy" the right annotation for the behavior we do here, where we're pulling
the native pointer out of the ObjC object and only storing that? Writing and
reading the property effectively produces a copy of the RTCMediaStreamTrack, so
I guess "copy" is reasonable...

[tkchin_webrtc, 2016/04/27 23:13:43]

Sort-of. Since we are overriding the setter these attributes are relatively
meaningless and only serve as a hint to the caller that we are not taking a ref
onto their object.

 
 @end
 
 RTC_EXPORT
 @interface RTCRtpSender : NSObject <RTCRtpSender>
 
 - (instancetype)init NS_UNAVAILABLE;
 
 @end
 
 NS_ASSUME_NONNULL_END