Add 2 more RTC_EXPORT.

The component build test failed close to the end of compilation because
of these two missing symbols, see [1].

[1] - https://ci.chromium.org/p/chromium/builders/try/win_chromium_compile_dbg_ng/435732

Bug: webrtc:9419
Change-Id: Ic46acf1acbf3bc04e7410f8d9858785739ca98d6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159683
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29766}
diff --git a/api/video_codecs/video_encoder.h b/api/video_codecs/video_encoder.h
index a112f26..bd18a22 100644
--- a/api/video_codecs/video_encoder.h
+++ b/api/video_codecs/video_encoder.h
@@ -225,7 +225,7 @@
     bool supports_simulcast;
   };
 
-  struct RateControlParameters {
+  struct RTC_EXPORT RateControlParameters {
     RateControlParameters();
     RateControlParameters(const VideoBitrateAllocation& bitrate,
                           double framerate_fps);
diff --git a/p2p/stunprober/stun_prober.h b/p2p/stunprober/stun_prober.h
index bdfb758..a739a6c 100644
--- a/p2p/stunprober/stun_prober.h
+++ b/p2p/stunprober/stun_prober.h
@@ -67,7 +67,7 @@
     virtual void OnFinished(StunProber* prober, StunProber::Status status) = 0;
   };
 
-  struct Stats {
+  struct RTC_EXPORT Stats {
     Stats();
     ~Stats();