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

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaStreamTrack.h

 /*
  *  Copyright 2015 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>
 
 /**
  * Represents the state of the track. This exposes the same states in C++.
  */
 typedef NS_ENUM(NSInteger, RTCMediaStreamTrackState) {
   RTCMediaStreamTrackStateLive,
   RTCMediaStreamTrackStateEnded
 };
 
 NS_ASSUME_NONNULL_BEGIN
 
 RTC_EXPORT

[tkchin_webrtc, 2016/04/28 00:05:27]

RTC_EXPORT must be placed immediately before @interface

[skvlad, 2016/04/28 00:23:44]

Oops, sorry - I somehow mistook it for the NS_ASSUME_NONNULL_BEGIN macro. 

+
+extern NSString * const kRTCMediaStreamTrackKindAudio;

[tkchin_webrtc, 2016/04/28 00:05:27]

RTC_EXTERN

[skvlad, 2016/04/28 00:23:44]

Done.

+extern NSString * const kRTCMediaStreamTrackKindVideo;
+
 @interface RTCMediaStreamTrack : NSObject
 
 /**
  * The kind of track. For example, "audio" if this track represents an audio
  * track and "video" if this track represents a video track.
  */
 @property(nonatomic, readonly) NSString *kind;
 
 /** An identifier string. */
 @property(nonatomic, readonly) NSString *trackId;
 
 /** The enabled state of the track. */
 @property(nonatomic, assign) BOOL isEnabled;
 
 /** The state of the track. */
 @property(nonatomic, readonly) RTCMediaStreamTrackState readyState;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 @end
 
 NS_ASSUME_NONNULL_END