chromeos: Run beforeunload handlers when closing panels.

chrome/browser/chromeos/frame/panel_controller.h

 // Copyright (c) 2010 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_CHROMEOS_FRAME_PANEL_CONTROLLER_H_
 #define CHROME_BROWSER_CHROMEOS_FRAME_PANEL_CONTROLLER_H_
 #pragma once
 
 #include <gtk/gtk.h>
 
@@ skipping 26 matching lines @@
 
   // Delegate to control panel's appearance and behavior.
   class Delegate {
    public:
     // Retrieves the title string of the panel.
     virtual string16 GetPanelTitle() = 0;
 
     // Retrieves the icon to use in the panel's titlebar.
     virtual SkBitmap GetPanelIcon() = 0;
 
+    // Can the panel be closed?  Called before ClosePanel() when the close
+    // button is pressed to give beforeunload handlers a chance to cancel.
+    virtual bool CanClosePanel() = 0;
+
     // Close the panel. Called when a close button is pressed.
     virtual void ClosePanel() = 0;
   };
 
   PanelController(Delegate* delegate_window,
                   GtkWindow* window);
   virtual ~PanelController() {}
 
   // Initializes the panel controller with the initial state of the focus and
   // the window bounds.
@@ skipping 89 matching lines @@
 
   // GTK client event handler id.
   int client_event_handler_id_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelController);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FRAME_PANEL_CONTROLLER_H_