Cleanup: Pass std::string as const reference from native_client_sdk/

native_client_sdk/src/examples/api/file_io/file_io.cc

 // 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.
 
 /// @file file_io.cc
 /// This example demonstrates the use of persistent file I/O
 
 #define __STDC_LIMIT_MACROS
 #include <stdio.h>
 
@@ skipping 82 matching lines @@
       message.Set(i + 1, strings[i]);
     }
 
     PostMessage(message);
   }
 
   void PostArrayMessage(const char* command) {
     PostArrayMessage(command, StringVector());
   }
 
-  void PostArrayMessage(const char* command, std::string s) {
+  void PostArrayMessage(const char* command, const std::string& s) {
     StringVector sv;
     sv.push_back(s);
     PostArrayMessage(command, sv);
   }
 
   /// Handler for messages coming in from the browser via postMessage().  The
   /// @a var_message can contain anything: a JSON string; a string that encodes
   /// method names and arguments; etc.
   ///
   /// Here we use messages to communicate with the user interface
@@ skipping 270 matching lines @@
 };
 
 namespace pp {
 /// Factory function called by the browser when the module is first loaded.
 /// The browser keeps a singleton of this module.  It calls the
 /// CreateInstance() method on the object you return to make instances.  There
 /// is one instance per <embed> tag on the page.  This is the main binding
 /// point for your NaCl module with the browser.
 Module* CreateModule() { return new FileIoModule(); }
 }  // namespace pp