Cleanup: Pass std::string as const reference if possible

chromeos/network/network_connection_handler.cc

 // Copyright (c) 2013 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 "chromeos/network/network_connection_handler.h"
 
 #include "base/bind.h"
 #include "base/json/json_reader.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 638 matching lines @@
     error = kErrorConnecting;
   } else {
     NET_LOG_ERROR("Connect Failure, Shill error: " + dbus_error_name,
                   service_path);
     error = kErrorConnectFailed;
   }
   InvokeConnectErrorCallback(service_path, error_callback, error);
 }
 
 void NetworkConnectionHandler::CheckPendingRequest(
-    const std::string service_path) {
+    const std::string& service_path) {
   ConnectRequest* request = GetPendingRequest(service_path);
   DCHECK(request);
   if (request->connect_state == ConnectRequest::CONNECT_REQUESTED)
     return;  // Request has not started, ignore update
   const NetworkState* network =
       network_state_handler_->GetNetworkState(service_path);
   if (!network)
     return;  // NetworkState may not be be updated yet.
 
   if (network->IsConnectingState()) {
@@ skipping 102 matching lines @@
 
 void NetworkConnectionHandler::HandleShillDisconnectSuccess(
     const std::string& service_path,
     const base::Closure& success_callback) {
   NET_LOG_EVENT("Disconnect Request Sent", service_path);
   if (!success_callback.is_null())
     success_callback.Run();
 }
 
 }  // namespace chromeos