if (aFrameList) { mFrames.AppendFrames(this, aFrameList); return ChildListChanged(aPresContext, nsIDOMMutationEvent::ADDITION); } return NS_OK; }
nsMathMLContainerFrame::AppendFrames(nsIPresContext* aPresContext,                                     nsIPresShell&   aPresShell,                                     nsIAtom*        aListName,                                     nsIFrame*       aFrameList){  if (aListName) {    return NS_ERROR_INVALID_ARG;  }  if (aFrameList) {    mFrames.AppendFrames(this, aFrameList);    return ChildListChanged(aPresContext, nsIDOMMutationEvent::ADDITION);  }  return NS_OK;}