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

chromeos/network/network_connection_handler.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROMEOS_NETWORK_NETWORK_CONNECTION_HANDLER_H_
 #define CHROMEOS_NETWORK_NETWORK_CONNECTION_HANDLER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 175 matching lines @@
       const std::string& service_path,
       const std::string& error_name,
       scoped_ptr<base::DictionaryValue> error_data);
 
   // Handles success or failure from Shill.Service.Connect.
   void HandleShillConnectSuccess(const std::string& service_path);
   void HandleShillConnectFailure(const std::string& service_path,
                                  const std::string& error_name,
                                  const std::string& error_message);
 
-  void CheckPendingRequest(const std::string service_path);
+  void CheckPendingRequest(const std::string& service_path);
   void CheckAllPendingRequests();
 
   // Notify caller and observers that the connect request succeeded.
   void InvokeConnectSuccessCallback(const std::string& service_path,
                                     const base::Closure& success_callback);
 
   // Look up the ConnectRequest for |service_path| and call
   // InvokeConnectErrorCallback.
   void ErrorCallbackForPendingRequest(const std::string& service_path,
                                       const std::string& error_name);
@@ skipping 32 matching lines @@
   bool logged_in_;
   bool certificates_loaded_;
   base::TimeTicks logged_in_time_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkConnectionHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_NETWORK_CONNECTION_HANDLER_H_