Mark public ObjC APIs as explicitly visible.

webrtc/api/objc/RTCPeerConnectionFactory.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/base/objc/RTCMacros.h"
+
 NS_ASSUME_NONNULL_BEGIN
 
 @class RTCAVFoundationVideoSource;
 @class RTCAudioTrack;
 @class RTCConfiguration;
 @class RTCMediaConstraints;
 @class RTCMediaStream;
 @class RTCPeerConnection;
 @class RTCVideoSource;
 @class RTCVideoTrack;
 @protocol RTCPeerConnectionDelegate;
 
+RTC_EXPORT
 @interface RTCPeerConnectionFactory : NSObject
 
 - (instancetype)init NS_DESIGNATED_INITIALIZER;
 
 /** Initialize an RTCAVFoundationVideoSource with constraints. */
 - (RTCAVFoundationVideoSource *)avFoundationVideoSourceWithConstraints:
     (nullable RTCMediaConstraints *)constraints;
 
 /** Initialize an RTCAudioTrack with an id. */
 - (RTCAudioTrack *)audioTrackWithTrackId:(NSString *)trackId;
@@ skipping 11 matching lines @@
 - (RTCPeerConnection *)peerConnectionWithConfiguration:
     (RTCConfiguration *)configuration
                                            constraints:
     (RTCMediaConstraints *)constraints
                                               delegate:
     (nullable id<RTCPeerConnectionDelegate>)delegate;
 
 @end
 
 NS_ASSUME_NONNULL_END