Mark public ObjC APIs as explicitly visible.

webrtc/api/objc/RTCDataChannel.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 <AvailabilityMacros.h>
 #import <Foundation/Foundation.h>
 
+#import "webrtc/base/objc/RTCMacros.h"
+
 NS_ASSUME_NONNULL_BEGIN
 
+RTC_EXPORT
 @interface RTCDataBuffer : NSObject
 
 /** NSData representation of the underlying buffer. */
 @property(nonatomic, readonly) NSData *data;
 
 /** Indicates whether |data| contains UTF-8 or binary data. */
 @property(nonatomic, readonly) BOOL isBinary;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 /**
  * Initialize an RTCDataBuffer from NSData. |isBinary| indicates whether |data|
  * contains UTF-8 or binary data.
  */
 - (instancetype)initWithData:(NSData *)data isBinary:(BOOL)isBinary;
 
 @end
 
 
 @class RTCDataChannel;
+RTC_EXPORT
 @protocol RTCDataChannelDelegate <NSObject>
 
 /** The data channel state changed. */
 - (void)dataChannelDidChangeState:(RTCDataChannel *)dataChannel;
 
 /** The data channel successfully received a data buffer. */
 - (void)dataChannel:(RTCDataChannel *)dataChannel
     didReceiveMessageWithBuffer:(RTCDataBuffer *)buffer;
 
 @optional
 /** The data channel's |bufferedAmount| changed. */
 - (void)dataChannel:(RTCDataChannel *)dataChannel
     didChangeBufferedAmount:(uint64_t)amount;
 
 @end
 
 
 /** Represents the state of the data channel. */
 typedef NS_ENUM(NSInteger, RTCDataChannelState) {
   RTCDataChannelStateConnecting,
   RTCDataChannelStateOpen,
   RTCDataChannelStateClosing,
   RTCDataChannelStateClosed,
 };
 
-
+RTC_EXPORT
 @interface RTCDataChannel : NSObject
 
 /**
  * A label that can be used to distinguish this data channel from other data
  * channel objects.
  */
 @property(nonatomic, readonly) NSString *label;
 
 /** Whether the data channel can send messages in unreliable mode. */
 @property(nonatomic, readonly) BOOL isReliable DEPRECATED_ATTRIBUTE;
@@ skipping 49 matching lines @@
 
 /** Closes the data channel. */
 - (void)close;
 
 /** Attempt to send |data| on this data channel's underlying data transport. */
 - (BOOL)sendData:(RTCDataBuffer *)data;
 
 @end
 
 NS_ASSUME_NONNULL_END