Comment 3 for bug 510529

If the user wants to do that, they could click "save as draft", and then close the message in the same number of clicks... this would be a positive action rather than relying on the client to remind them of somthing they have forgotten.

If no changes are made between when the window is opened, and when it is closed, i don't believe that it should delay the close with a dialog which is primarily asking if you want to discard your changes.