Drarry and the deathly hallows

Draco accepts dumbledores offer of help in the astronomy tower and is put under the protection of harry potter. He goes with harry, ron and hermione on the hocrux hunt. How will the story change? ( Im not really sticking to the events from the movie or the book so it will not be exactly the same. This is boy boy. dont like dont read. please no nasty comments there will be no smut.)