wstrings: convert CppVariant and CppBoundClass to not use wstring

chrome/renderer/external_host_bindings.h

 // Copyright (c) 2006-2008 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 CHROME_RENDERER_EXTERNAL_HOST_BINDINGS_H_
 #define CHROME_RENDERER_EXTERNAL_HOST_BINDINGS_H_
 #pragma once
 
 #include "chrome/renderer/dom_ui_bindings.h"
 #include "ipc/ipc_message.h"
@@ skipping 11 matching lines @@
   // The postMessage() function provided to Javascript.
   void postMessage(const CppArgumentList& args, CppVariant* result);
 
   // Invokes the registered onmessage handler.
   // Returns true on successful invocation.
   bool ForwardMessageFromExternalHost(const std::string& message,
                                       const std::string& origin,
                                       const std::string& target);
 
   // Overridden to hold onto a pointer back to the web frame.
-  void BindToJavascript(WebKit::WebFrame* frame,
-                        const std::wstring& classname) {
+  void BindToJavascript(WebKit::WebFrame* frame, const std::string& classname) {
     frame_ = frame;
     DOMBoundBrowserObject::BindToJavascript(frame, classname);
   }
 
  protected:
   // Creates an uninitialized instance of a MessageEvent object.
   // This is equivalent to calling window.document.createEvent("MessageEvent")
   // in javascript.
   bool CreateMessageEvent(NPObject** message_event);
 
  private:
   CppVariant on_message_handler_;
   WebKit::WebFrame* frame_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalHostBindings);
 };
 
 #endif  // CHROME_RENDERER_EXTERNAL_HOST_BINDINGS_H_