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/rtc_base/async_packet_socket.h b/rtc_base/async_packet_socket.h
index 3afff3b..50c07e2 100644
--- a/rtc_base/async_packet_socket.h
+++ b/rtc_base/async_packet_socket.h
@@ -15,6 +15,7 @@
 #include "rtc_base/dscp.h"
 #include "rtc_base/network/sent_packet.h"
 #include "rtc_base/socket.h"
+#include "rtc_base/system/rtc_export.h"
 #include "rtc_base/third_party/sigslot/sigslot.h"
 #include "rtc_base/time_utils.h"
 
@@ -36,7 +37,7 @@
 
 // This structure holds meta information for the packet which is about to send
 // over network.
-struct PacketOptions {
+struct RTC_EXPORT PacketOptions {
   PacketOptions();
   explicit PacketOptions(DiffServCodePoint dscp);
   PacketOptions(const PacketOptions& other);
@@ -53,7 +54,7 @@
 
 // Provides the ability to receive packets asynchronously. Sends are not
 // buffered since it is acceptable to drop packets under high load.
-class AsyncPacketSocket : public sigslot::has_slots<> {
+class RTC_EXPORT AsyncPacketSocket : public sigslot::has_slots<> {
  public:
   enum State {
     STATE_CLOSED,