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/base/objc/RTCMacros.h b/webrtc/base/objc/RTCMacros.h
index 4979a2b..f9f15c3 100644
--- a/webrtc/base/objc/RTCMacros.h
+++ b/webrtc/base/objc/RTCMacros.h
@@ -11,10 +11,12 @@
#ifndef WEBRTC_BASE_OBJC_RTC_MACROS_H_
#define WEBRTC_BASE_OBJC_RTC_MACROS_H_
+#define RTC_EXPORT __attribute__((visibility("default")))
+
#if defined(__cplusplus)
-#define RTC_EXPORT extern "C"
+#define RTC_EXTERN extern "C" RTC_EXPORT
#else
-#define RTC_EXPORT extern
+#define RTC_EXTERN extern RTC_EXPORT
#endif
#ifdef __OBJC__