Relanding Generate localhost candidate when no STUN/TURN and portallocator has the right flag spefi…

webrtc/base/ipaddress.cc

Index: webrtc/base/ipaddress.cc
diff --git a/webrtc/base/ipaddress.cc b/webrtc/base/ipaddress.cc
index 768a7092a3c797db17c86748cc15b9387cd3a1dd..3dd856a64abc817ac8de32d22e04a85ccaa74cab 100644
--- a/webrtc/base/ipaddress.cc
+++ b/webrtc/base/ipaddress.cc
@@ -498,4 +498,13 @@ int IPAddressPrecedence(const IPAddress& ip) {
   return 0;
 }
 
-}  // Namespace talk base
+IPAddress GetLoopbackIP(int family) {
+  if (family == AF_INET) {
+    return rtc::IPAddress(INADDR_LOOPBACK);
+  }
+  if (family == AF_INET6) {
+    return rtc::IPAddress(in6addr_loopback);
+  }
+  return rtc::IPAddress();
+}
+}  // Namespace rtc