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/jsep.h b/api/jsep.h
index 3f7f12a..7b4934a 100644
--- a/api/jsep.h
+++ b/api/jsep.h
@@ -52,7 +52,7 @@
 // a time and is therefore not expected to be thread safe.
 //
 // An instance can be created by CreateIceCandidate.
-class IceCandidateInterface {
+class RTC_EXPORT IceCandidateInterface {
  public:
   virtual ~IceCandidateInterface() {}
   // If present, this is the value of the "a=mid" attribute of the candidate's