Remove usage of FOR_EACH_OBSERVER macro in blimp

blimp/net/blimp_connection.cc

Index: blimp/net/blimp_connection.cc
diff --git a/blimp/net/blimp_connection.cc b/blimp/net/blimp_connection.cc
index cc5f855fa24453fef1db8d5dc77d249f4ffe64b4..57a3580d74394de21c9ab30ecba1141a29171e29 100644
--- a/blimp/net/blimp_connection.cc
+++ b/blimp/net/blimp_connection.cc
@@ -192,8 +192,8 @@ void BlimpConnection::OnConnectionError(int error) {
   VLOG(1) << "OnConnectionError, error=" << error;
 
   // Propagate the error to all observers.
-  FOR_EACH_OBSERVER(ConnectionErrorObserver, error_observers_,
-                    OnConnectionError(error));
+  for (auto& observer : error_observers_)
+    observer.OnConnectionError(error);
 }
 
 }  // namespace blimp