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/RTCVideoRenderer.h b/webrtc/api/objc/RTCVideoRenderer.h
index 2fe4efb..41c3e37 100644
--- a/webrtc/api/objc/RTCVideoRenderer.h
+++ b/webrtc/api/objc/RTCVideoRenderer.h
@@ -13,10 +13,13 @@
#import <UIKit/UIKit.h>
#endif
+#import "webrtc/base/objc/RTCMacros.h"
+
NS_ASSUME_NONNULL_BEGIN
@class RTCVideoFrame;
+RTC_EXPORT
@protocol RTCVideoRenderer <NSObject>
/** The size of the frame. */