[css3-background] border-image and the border shorthand

If an image border and a non-image border are both specified on an element,
the image border always wins over the non-image border. In a lot of cases
this makes sense, as you are specifying them together and the non-image
border is meant as a fallback:

   .super-sale {
      border: solid red;
      border-image: url(ragged-edge.svg) 25%;
   }

But when you have multiple elements and classes and you're using the
cascade, if a declaration further back in the cascade uses border-image

   .sidebox {
      border: thin silver;
      border-image: url(cartouche) 25%;
   }

and a more specific declaration wants to set a different border

   #message-box {
     border: none;
     border-radius: 0.5em;
     box-shadow: 0.3em 0.3em;
   }

unless it resets border-image, that new border style will have no effect.

So I'm thinking maybe the 'border' shorthand should reset border-image,
so that when you use it you know you're starting with a blank canvas.

Thoughts?

~fantasai