Export symbols needed by the Chromium component build (part 3).

This CL uses RTC_EXPORT (defined in rtc_base/system/rtc_export.h)
to mark WebRTC symbols as visible from a shared library, this doesn't
mean these symbols are part of the public API (please continue to refer
to [1] for info about what is considered public WebRTC API).

Bug: webrtc:9419
Change-Id: I4d4e2ae52ee01de68147fd0f2cfe4c92d600ad94
Reviewed-on: https://webrtc-review.googlesource.com/c/106343
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25207}
diff --git a/api/peerconnectioninterface.h b/api/peerconnectioninterface.h
index 141b2c9..8775cf0 100644
--- a/api/peerconnectioninterface.h
+++ b/api/peerconnectioninterface.h
@@ -113,6 +113,7 @@
 #include "rtc_base/socketaddress.h"
 #include "rtc_base/sslcertificate.h"
 #include "rtc_base/sslstreamadapter.h"
+#include "rtc_base/system/rtc_export.h"
 
 namespace rtc {
 class SSLIdentity;
@@ -1376,7 +1377,8 @@
 // be created and used.
 // If |network_controller_factory| is provided, it will be used if enabled via
 // field trial.
-rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
+RTC_EXPORT rtc::scoped_refptr<PeerConnectionFactoryInterface>
+CreatePeerConnectionFactory(
     rtc::Thread* network_thread,
     rtc::Thread* worker_thread,
     rtc::Thread* signaling_thread,