Backed out changeset 18b48ea2b188

to fix Bug 454186
SM crashes when try to download file [@ nsString::ToInteger - nsTreeBodyFrame::PaintProgressMeter]

layout/generic/nsContainerFrame.cpp

@@ -1099,11 +1099,7 @@ void
 nsContainerFrame::DeleteNextInFlowChild(nsPresContext* aPresContext,
                                         nsIFrame*      aNextInFlow)
 {
-#ifdef DEBUG
-  nsIFrame* prevInFlow = aNextInFlow->GetPrevInFlow();
-#endif
-
-  NS_PRECONDITION(prevInFlow, "bad prev-in-flow");
+  NS_PRECONDITION(aNextInFlow->GetPrevInFlow(), "bad prev-in-flow");
 
   // If the next-in-flow has a next-in-flow then delete it, too (and
   // delete it first).