PRInt32         aModType,
CanvasFrame::AttributeChanged(nsIPresContext* aPresContext,                          nsIContent*     aChild,                          PRInt32         aNameSpaceID,                          nsIAtom*        aAttribute,                          PRInt32         aHint){// if the background color or image is changing, invalidate the canvas  if (aHint > 0){    if (aAttribute == nsHTMLAtoms::bgcolor ||        aAttribute == nsHTMLAtoms::background) {      Invalidate(aPresContext,mRect,PR_FALSE);    }  }  return NS_OK;}