Remove usage of base::ObserverList<T>::Iter::GetNext() in //remoting.

remoting/signaling/xmpp_signal_strategy.cc

Index: remoting/signaling/xmpp_signal_strategy.cc
diff --git a/remoting/signaling/xmpp_signal_strategy.cc b/remoting/signaling/xmpp_signal_strategy.cc
index 2dad2f71616a44104d95ab1d173ed4aa5c5bf736..591dac2c4b907bd5cd7236d8ead0c90f6abbddc1 100644
--- a/remoting/signaling/xmpp_signal_strategy.cc
+++ b/remoting/signaling/xmpp_signal_strategy.cc
@@ -366,9 +366,8 @@ void XmppSignalStrategy::Core::OnStanza(
             << stanza->Str()
             << "\n=========================================================";
 
-  base::ObserverListBase<Listener>::Iterator it(&listeners_);
-  for (Listener* listener = it.GetNext(); listener; listener = it.GetNext()) {
-    if (listener->OnSignalStrategyIncomingStanza(stanza.get()))
+  for (auto& listener : listeners_) {
+    if (listener.OnSignalStrategyIncomingStanza(stanza.get()))
       return;
   }
 }