Makes the current page dim out when transitioning to instant preview.

chrome/browser/gtk/browser_window_gtk.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_GTK_BROWSER_WINDOW_GTK_H_
 #define CHROME_BROWSER_GTK_BROWSER_WINDOW_GTK_H_
 #pragma once
 
 #include <gtk/gtk.h>
 
@@ skipping 107 matching lines @@
                             bool show_history);
   virtual void ShowAppMenu();
   virtual bool PreHandleKeyboardEvent(const NativeWebKeyboardEvent& event,
                                       bool* is_keyboard_shortcut);
   virtual void HandleKeyboardEvent(const NativeWebKeyboardEvent& event);
   virtual void ShowCreateShortcutsDialog(TabContents* tab_contents);
   virtual void Cut();
   virtual void Copy();
   virtual void Paste();
   virtual void ToggleTabStripMode() {}
+  virtual void PrepareForInstant();
   virtual void ShowInstant(TabContents* preview_contents);
   virtual void HideInstant();
   virtual gfx::Rect GetInstantBounds();
 
   // Overridden from NotificationObserver:
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
   // Overridden from TabStripModelObserver:
@@ skipping 338 matching lines @@
   scoped_ptr<FullscreenExitBubbleGtk> fullscreen_exit_bubble_;
 
   // The model that tracks the paint state of the arrow for the infobar
   // directly below the toolbar.
   InfoBarArrowModel infobar_arrow_model_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserWindowGtk);
 };
 
 #endif  // CHROME_BROWSER_GTK_BROWSER_WINDOW_GTK_H_