Add missing GetFirstInFlow() call that was causing a crash in ComputeDescendantWidth when printing with font inflation enabled (or a debug build). (Bug 751797) r=roc

--HG--
extra : transplant_source : %ED%23%02%AFR%24tw%FE%96%D7%D3p%D8%87%F7gV%28L

layout/generic/nsFontInflationData.cpp

@@ -159,7 +159,7 @@ ComputeDescendantWidth(const nsHTMLReflowState& aAncestorReflowState,
 
   AutoInfallibleTArray<nsIFrame*, 16> frames;
   for (nsIFrame *f = aDescendantFrame; f != ancestorFrame;
-       f = f->GetParent()) {
+       f = f->GetParent()->GetFirstInFlow()) {
     frames.AppendElement(f);
   }