Try to add more sanity checking to help track down a crash....

chrome/browser/views/autocomplete/autocomplete_popup_win.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_VIEWS_AUTOCOMPLETE_AUTOCOMPLETE_POPUP_WIN_H_
 #define CHROME_BROWSER_VIEWS_AUTOCOMPLETE_AUTOCOMPLETE_POPUP_WIN_H_
 
 #include "views/widget/widget_win.h"
 
 class AutocompleteEditView;
 class AutocompletePopupContentsView;
 
 class AutocompletePopupWin : public views::WidgetWin {
  public:
   explicit AutocompletePopupWin(AutocompletePopupContentsView* contents);
   virtual ~AutocompletePopupWin();
 
+  // Overridden from WidgetWin:
+  virtual void Show();
+  virtual void Hide();
+
   // Creates the popup and shows it for the first time. |edit_view| is the edit
   // that created us.
   void Init(AutocompleteEditView* edit_view, views::View* contents);
 
-  // Shows the popup and moves it to the right position.
-  void Show();
-
   // Returns true if the popup is open.
   bool IsOpen() const;
 
   // Returns true if the popup has been created.
   bool IsCreated() const;
 
  protected:
   // Overridden from WidgetWin:
   virtual LRESULT OnMouseActivate(HWND window,
                                   UINT hit_test,
                                   UINT mouse_message);
 
  private:
   AutocompletePopupContentsView* contents_;
 
+  bool is_open_;  // Used only for sanity-checking.
+
   DISALLOW_COPY_AND_ASSIGN(AutocompletePopupWin);
 };
 
 #endif  // #ifndef CHROME_BROWSER_VIEWS_AUTOCOMPLETE_AUTOCOMPLETE_POPUP_WIN_H_