[XBL] Provide Example for section 5.1

In section 5.1, can you please break up the following paragraph into at
least 2 sentences. It is currently hard to follow:

 

"The xblEnteredDocument() method is called by the user agent when the
bound element, or one of its ancestors, or one of the elements in a
higher shadow scope, is inserted into the document, and when the binding
is originally attached, if the bound element is already in the
document."

 

Can you please also provide an example for xblEnteredDocument in the
same section.

Marcos