Add 3 missing RTC_EXPORT.

These two annotations are now needed to correctly compile Chromium
with is_component_build=true and the WebRTC component.

TBR: kwiberg@webrtc.org
Bug: webrtc:9419
Change-Id: Id5603cf747357c0c2a4b41684eb4fd607cccfdea
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158881
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29686}
diff --git a/pc/sdp_utils.h b/pc/sdp_utils.h
index 5e765fa..fc4b289 100644
--- a/pc/sdp_utils.h
+++ b/pc/sdp_utils.h
@@ -17,17 +17,18 @@
 
 #include "api/jsep.h"
 #include "pc/session_description.h"
+#include "rtc_base/system/rtc_export.h"
 
 namespace webrtc {
 
 // Returns a copy of the given session description.
-std::unique_ptr<SessionDescriptionInterface> CloneSessionDescription(
+RTC_EXPORT std::unique_ptr<SessionDescriptionInterface> CloneSessionDescription(
     const SessionDescriptionInterface* sdesc);
 
 // Returns a copy of the given session description with the type changed.
-std::unique_ptr<SessionDescriptionInterface> CloneSessionDescriptionAsType(
-    const SessionDescriptionInterface* sdesc,
-    SdpType type);
+RTC_EXPORT std::unique_ptr<SessionDescriptionInterface>
+CloneSessionDescriptionAsType(const SessionDescriptionInterface* sdesc,
+                              SdpType type);
 
 // Function that takes a single session description content with its
 // corresponding transport and produces a boolean.