Automatically accept any beforeunload prompt upon navigation or close…

… window. (w3c#1782)

index.html

@@ -9984,7 +9984,7 @@ <h2>User prompts</h2>
 
 <p><a>User prompts</a> that are spawned
  from <a><code>beforeunload</code></a> event handlers,
- are <a>dismissed</a> implicitly upon <a>navigation</a>
+ are <a>accepted</a> implicitly upon <a>navigation</a>
  or <a>close window</a>,
  regardless of the defined <a>user prompt handler</a>.