aFrame->GetProperty(nsLayoutAtoms::IBSplitSpecialPrevSibling, &rv));
aPresContext->FrameManager()->GetFrameProperty(aFrame, nsLayoutAtoms::IBSplitSpecialPrevSibling, 0, &rv));
GetIBSpecialSibling(nsPresContext* aPresContext,                    nsIFrame* aFrame,                    nsIFrame** aSpecialSibling){  NS_PRECONDITION(aFrame, "Must have a non-null frame!");  NS_ASSERTION(aFrame->GetStateBits() & NS_FRAME_IS_SPECIAL,               "GetIBSpecialSibling should not be called on a non-special frame");    // Find the first-in-flow of the frame.  (Ugh.  This ends up  // being O(N^2) when it is called O(N) times.)  aFrame = aFrame->GetFirstInFlow();  /*   * Now look up the nsLayoutAtoms::IBSplitSpecialPrevSibling   * property, which is only set on the anonymous block frames we're   * interested in.   */  nsresult rv;  nsIFrame *specialSibling = NS_STATIC_CAST(nsIFrame*,           aFrame->GetProperty(nsLayoutAtoms::IBSplitSpecialPrevSibling, &rv));  if (NS_OK == rv) {    NS_ASSERTION(specialSibling, "null special sibling");    *aSpecialSibling = specialSibling;  }  return NS_OK;}