Update API for Objective-C RTCMediaStream.

webrtc/api/objc/RTCMediaStream.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>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class RTCAudioTrack;
+@class RTCVideoTrack;
+
+@interface RTCMediaStream : NSObject
+
+/** The audio tracks in this stream. */
+@property(nonatomic, strong, readonly) NSArray<RTCAudioTrack *> *audioTracks;
+
+/** The video tracks in this stream. */
+@property(nonatomic, strong, readonly) NSArray<RTCVideoTrack *> *videoTracks;
+
+/** An identifier for this media stream. */
+@property(nonatomic, readonly) NSString *streamId;
+
+- (instancetype)init NS_UNAVAILABLE;
+
+/** Adds the given audio track to this media stream. */
+- (void)addAudioTrack:(RTCAudioTrack *)audioTrack;
+
+/** Adds the given video track to this media stream. */
+- (void)addVideoTrack:(RTCVideoTrack *)videoTrack;
+
+/** Removes the given audio track to this media stream. */
+- (void)removeAudioTrack:(RTCAudioTrack *)audioTrack;
+
+/** Removes the given video track to this media stream. */
+- (void)removeVideoTrack:(RTCVideoTrack *)videoTrack;
+
+@end
+
+NS_ASSUME_NONNULL_END