[XHTML 2] 15 Bi-directional text collection and embedded attributes?

Dear HTML Working Group,

http://www.w3.org/TR/xhtml2/mod-bidi.html#col_Bi-directional

says that the dir attribute specifies the direction of the elements text 
content, what is the elements text content in the case of embedded 
attributes?

ie how is <p dir="ltr" src="data:text/plain;chickens"/> rendered?

Regards,

Jim Ley