It turns out the Cleanup() method in JsModalDialog is not

chrome/browser/ui/app_modal_dialogs/js_modal_dialog.cc

 // 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.
 
 #include "chrome/browser/ui/app_modal_dialogs/js_modal_dialog.h"
 
 #include "base/string_util.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/extensions/extension_host.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
@@ skipping 97 matching lines @@
   // that were still open in the ModalDialogQueue, which would send activation
   // back to this one. The framework should be improved to handle this, so this
   // is a temporary workaround.
   CompleteDialog();
 
   if (!skip_this_dialog_) {
     delegate_->OnMessageBoxClosed(reply_msg_, false, std::wstring());
     if (suppress_js_messages)
       delegate_->SetSuppressMessageBoxes(true);
   }
-
-  Cleanup();
 }
 
 void JavaScriptAppModalDialog::OnAccept(const std::wstring& prompt_text,
                                         bool suppress_js_messages) {
   CompleteDialog();
 
   if (!skip_this_dialog_) {

[Matt Perry, 2010/12/03 00:39:22]

maybe this block is what should go into Cleanup.

     delegate_->OnMessageBoxClosed(reply_msg_, true, prompt_text);
     if (suppress_js_messages)
       delegate_->SetSuppressMessageBoxes(true);
   }
-
-  Cleanup();
 }
 
 void JavaScriptAppModalDialog::OnClose() {
-  Cleanup();
-}
-
-void JavaScriptAppModalDialog::Cleanup() {
-  if (skip_this_dialog_) {
-    // We can't use the |delegate_|, because we might be in the process of
-    // destroying it.
-    if (tab_contents_)
-      tab_contents_->OnMessageBoxClosed(reply_msg_, false, L"");
-// The extension_host_ will always be a dirty pointer on OS X because the alert
-// window will cause the extension popup to close since it is resigning its key
-// state, destroying the host. http://crbug.com/29355
-#if !defined(OS_MACOSX)
-    else if (extension_host_)
-      extension_host_->OnMessageBoxClosed(reply_msg_, false, L"");
-    else
-      NOTREACHED();
-#endif
+  if (!skip_this_dialog_) {
+    delegate_->OnMessageBoxClosed(reply_msg_, true, L"");
+    // TODO(aa): It would be good to handle supress here, too, but we need to
+    // get passed the bit.
   }
 }