Fix handling of tab contents disappearing out from underneath Javascript dialogs.

chrome/browser/ui/app_modal_dialogs/message_box_handler.cc

Index: chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
diff --git a/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc b/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
index 861d0731d66fe057c3ffab6c4d4d39f20ca1435f..9dc374a865920d655aa5a567e003ff8f8b0bba00 100644
--- a/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
+++ b/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
@@ -174,6 +174,9 @@ string16 ChromeJavaScriptDialogCreator::GetTitle(TitleType title_type,
 void ChromeJavaScriptDialogCreator::CancelPendingDialogs(
     content::DialogDelegate* delegate) {
   AppModalDialogQueue* queue = AppModalDialogQueue::GetInstance();
+  AppModalDialog* active_dialog = queue->active_dialog();
+  if (active_dialog && active_dialog->delegate() == delegate)
+    active_dialog->Invalidate();
   for (AppModalDialogQueue::iterator i = queue->begin();
        i != queue->end(); ++i) {
     if ((*i)->delegate() == delegate)