[mojo-edk] Fix race in port closure

mojo/edk/system/ports/node.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/ports/node.h"
 
 #include <string.h>
 
 #include <utility>
 
@@ skipping 195 matching lines @@
     // port to allow the peer to have the opportunity to consume all inbound
     // messages before notifying the embedder that this port is closed.
     data.last_sequence_num = port->next_sequence_num_to_send - 1;
 
     peer_node_name = port->peer_node_name;
     peer_port_name = port->peer_port_name;
 
     // If the port being closed still has unread messages, then we need to take
     // care to close those ports so as to avoid leaking memory.
     port->message_queue.GetReferencedPorts(&referenced_port_names);
+
+    ErasePort_Locked(port_ref.name());
   }
 
   DVLOG(2) << "Sending ObserveClosure from " << port_ref.name() << "@" << name_
            << " to " << peer_port_name << "@" << peer_node_name;
 
-  ErasePort(port_ref.name());
-
   delegate_->ForwardMessage(
       peer_node_name,
       NewInternalMessage(peer_port_name, EventType::kObserveClosure, data));
 
   for (const auto& name : referenced_port_names) {
     PortRef ref;
     if (GetPort(name, &ref) == OK)
       ClosePort(ref);
   }
   return OK;
@@ skipping 1007 matching lines @@
 
   if (num_data_bytes)
     memcpy(header + 1, data, num_data_bytes);
 
   return message;
 }
 
 }  // namespace ports
 }  // namespace edk
 }  // namespace mojo