Add missing RTC_EXPORT for the component build.

Bug: webrtc:9419
Change-Id: I3225259fb4cc55e9820f590928795f4587f1e3cb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/153884
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29479}
diff --git a/api/media_stream_interface.h b/api/media_stream_interface.h
index 6150350..5fb73c9 100644
--- a/api/media_stream_interface.h
+++ b/api/media_stream_interface.h
@@ -145,8 +145,9 @@
 // PeerConnectionFactory::CreateVideoTrack can be used for creating a VideoTrack
 // that ensures thread safety and that all methods are called on the right
 // thread.
-class VideoTrackInterface : public MediaStreamTrackInterface,
-                            public rtc::VideoSourceInterface<VideoFrame> {
+class RTC_EXPORT VideoTrackInterface
+    : public MediaStreamTrackInterface,
+      public rtc::VideoSourceInterface<VideoFrame> {
  public:
   // Video track content hint, used to override the source is_screencast
   // property.
@@ -235,7 +236,7 @@
   ~AudioProcessorInterface() override = default;
 };
 
-class AudioTrackInterface : public MediaStreamTrackInterface {
+class RTC_EXPORT AudioTrackInterface : public MediaStreamTrackInterface {
  public:
   // TODO(deadbeef): Figure out if the following interface should be const or
   // not.