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

talk/app/webrtc/webrtcsession.cc

Index: talk/app/webrtc/webrtcsession.cc
diff --git a/talk/app/webrtc/webrtcsession.cc b/talk/app/webrtc/webrtcsession.cc
index fde45104d61ddfafee2791b1e297d164ab6425ac..be567b88b4a88ddc853833da7a329fc9e95612de 100644
--- a/talk/app/webrtc/webrtcsession.cc
+++ b/talk/app/webrtc/webrtcsession.cc
@@ -725,6 +725,13 @@ bool WebRtcSession::Initialize(
   }
   port_allocator()->set_candidate_filter(
       ConvertIceTransportTypeToCandidateFilter(rtc_configuration.type));
+
+  if (rtc_configuration.enable_localhost_ice_candidate) {
+    port_allocator()->set_flags(
+        port_allocator()->flags() |
+        cricket::PORTALLOCATOR_ENABLE_LOCALHOST_CANDIDATE);
+  }
+
   return true;
 }