Implement window.alert() and its cousins for extensions....

chrome/browser/jsmessage_box_handler.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_BROWSER_JSMESSAGE_BOX_HANDLER_H_
 #define CHROME_BROWSER_JSMESSAGE_BOX_HANDLER_H_
 
 #include <string>
 
 #include "ipc/ipc_message.h"
 
 class GURL;
+class JavaScriptMessageBoxClient;
 class TabContents;
 
 // Creates and runs a Javascript Message Box dialog.
 // The dialog type is specified within |dialog_flags|, the
 // default static display text is in |message_text| and if the dialog box is
 // a user input prompt() box, the default text for the text field is in
 // |default_prompt_text|. The result of the operation is returned using
 // |reply_msg|.
-void RunJavascriptMessageBox(TabContents* tab_contents,
+void RunJavascriptMessageBox(JavaScriptMessageBoxClient* client,
                              const GURL& frame_url,
                              int dialog_flags,
                              const std::wstring& message_text,
                              const std::wstring& default_prompt_text,
                              bool display_suppress_checkbox,
                              IPC::Message* reply_msg);
 
 // This will display a modal dialog box with a header and footer asking the
 // the user if they wish to navigate away from a page, with additional text
 // |message_text| between the header and footer. The users response is
 // returned to the renderer using |reply_msg|.
 void RunBeforeUnloadDialog(TabContents* tab_contents,
                            const std::wstring& message_text,
                            IPC::Message* reply_msg);
 
 #endif // CHROME_BROWSER_JSMESSAGE_BOX_HANDLER_H_