Mark public ObjC APIs as explicitly visible.
BUG=
Review URL: https://codereview.webrtc.org/1899573002
Cr-Commit-Position: refs/heads/master@{#12431}
diff --git a/webrtc/api/objc/RTCVideoFrame.h b/webrtc/api/objc/RTCVideoFrame.h
index b44bf73..e76a9b3 100644
--- a/webrtc/api/objc/RTCVideoFrame.h
+++ b/webrtc/api/objc/RTCVideoFrame.h
@@ -11,9 +11,12 @@
#import <AVFoundation/AVFoundation.h>
#import <Foundation/Foundation.h>
+#import "webrtc/base/objc/RTCMacros.h"
+
NS_ASSUME_NONNULL_BEGIN
// RTCVideoFrame is an ObjectiveC version of cricket::VideoFrame.
+RTC_EXPORT
@interface RTCVideoFrame : NSObject
/** Width without rotation applied. */