Enforce that only one constrained window is displayed at once per tab.

chrome/browser/gtk/constrained_window_gtk.h

 // Copyright (c) 2009 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_CONSTRAINED_WINDOW_GTK_H_
 #define CHROME_BROWSER_GTK_CONSTRAINED_WINDOW_GTK_H_
 
 #include "chrome/browser/tab_contents/constrained_window.h"
 
 #include "base/basictypes.h"
@@ skipping 14 matching lines @@
 };
 
 // Constrained window implementation for the GTK port. Unlike the Win32 system,
 // ConstrainedWindowGtk doesn't draw draggable fake windows and instead just
 // centers the dialog. It is thus an order of magnitude simpler.
 class ConstrainedWindowGtk : public ConstrainedWindow {
  public:
   virtual ~ConstrainedWindowGtk();
 
   // Overridden from ConstrainedWindow:
+  virtual void ShowConstrainedWindow();
   virtual void CloseConstrainedWindow();
 
   // Returns the TabContents that constrains this Constrained Window.
   TabContents* owner() const { return owner_; }
 
   // Returns the toplevel widget that displays this "window".
   GtkWidget* widget() { return border_.get(); }
 
   // Returns the View that we collaborate with to position ourselves.
   TabContentsViewGtk* ContainingView();
 
  private:
   friend class ConstrainedWindow;
 
   ConstrainedWindowGtk(TabContents* owner,
                        ConstrainedWindowGtkDelegate* delegate);
 
   // The TabContents that owns and constrains this ConstrainedWindow.
   TabContents* owner_;
 
   // The top level widget container that exports to our TabContentsViewGtk.
   OwnedWidgetGtk border_;
 
   // Delegate that provides the contents of this constrained window.
   ConstrainedWindowGtkDelegate* delegate_;
 
+  // Stores if |ShowConstrainedWindow()| has been called.
+  bool visible_;
+
   DISALLOW_COPY_AND_ASSIGN(ConstrainedWindowGtk);
 };
 
 #endif  // CHROME_BROWSER_GTK_CONSTRAINED_WINDOW_GTK_H_