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

content/shell/browser/shell.h

 // Copyright 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.
 #ifndef CONTENT_SHELL_BROWSER_SHELL_H_
 #define CONTENT_SHELL_BROWSER_SHELL_H_
 
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 82 matching lines @@
   // Used for content_browsertests. Called once.
   static void SetShellCreatedCallback(
       base::Callback<void(Shell*)> shell_created_callback);
 
   WebContents* web_contents() const { return web_contents_.get(); }
   gfx::NativeWindow window() { return window_; }
 
 #if defined(OS_MACOSX)
   // Public to be called by an ObjC bridge object.
   void ActionPerformed(int control);
-  void URLEntered(std::string url_string);
+  void URLEntered(const std::string& url_string);
 #elif defined(OS_ANDROID)
   // Registers the Android Java to native methods.
   static bool Register(JNIEnv* env);
 #endif
 
   // WebContentsDelegate
   WebContents* OpenURLFromTab(WebContents* source,
                               const OpenURLParams& params) override;
   void AddNewContents(WebContents* source,
                       WebContents* new_contents,
@@ skipping 140 matching lines @@
   static base::Callback<void(Shell*)> shell_created_callback_;
 
   // True if the destructur of Shell should post a quit closure on the current
   // message loop if the destructed Shell object was the last one.
   static bool quit_message_loop_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_BROWSER_SHELL_H_