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/network.h b/rtc_base/network.h
index d202f6e..a8608d9 100644
--- a/rtc_base/network.h
+++ b/rtc_base/network.h
@@ -23,6 +23,7 @@
 #include "rtc_base/mdns_responder_interface.h"
 #include "rtc_base/message_handler.h"
 #include "rtc_base/network_monitor.h"
+#include "rtc_base/system/rtc_export.h"
 #include "rtc_base/third_party/sigslot/sigslot.h"
 
 #if defined(WEBRTC_POSIX)
@@ -52,7 +53,7 @@
 // Utility function that attempts to determine an adapter type by an interface
 // name (e.g., "wlan0"). Can be used by NetworkManager subclasses when other
 // mechanisms fail to determine the type.
-AdapterType GetAdapterTypeFromName(const char* network_name);
+RTC_EXPORT AdapterType GetAdapterTypeFromName(const char* network_name);
 
 class DefaultLocalAddressProvider {
  public:
@@ -84,8 +85,8 @@
 //
 // This allows constructing a NetworkManager subclass on one thread and
 // passing it into an object that uses it on a different thread.
-class NetworkManager : public DefaultLocalAddressProvider,
-                       public MdnsResponderProvider {
+class RTC_EXPORT NetworkManager : public DefaultLocalAddressProvider,
+                                  public MdnsResponderProvider {
  public:
   typedef std::vector<Network*> NetworkList;
 
@@ -157,7 +158,7 @@
 };
 
 // Base class for NetworkManager implementations.
-class NetworkManagerBase : public NetworkManager {
+class RTC_EXPORT NetworkManagerBase : public NetworkManager {
  public:
   NetworkManagerBase();
   ~NetworkManagerBase() override;
@@ -215,9 +216,9 @@
 
 // Basic implementation of the NetworkManager interface that gets list
 // of networks using OS APIs.
-class BasicNetworkManager : public NetworkManagerBase,
-                            public MessageHandler,
-                            public sigslot::has_slots<> {
+class RTC_EXPORT BasicNetworkManager : public NetworkManagerBase,
+                                       public MessageHandler,
+                                       public sigslot::has_slots<> {
  public:
   BasicNetworkManager();
   ~BasicNetworkManager() override;
@@ -290,7 +291,7 @@
 };
 
 // Represents a Unix-type network interface, with a name and single address.
-class Network {
+class RTC_EXPORT Network {
  public:
   Network(const std::string& name,
           const std::string& description,