Bug 1065868 - Make nsStyleMargin::MaxDifference return the right bits. r=dbaron

layout/style/nsStyleStruct.h

@@ -593,9 +593,8 @@ struct nsStyleMargin {
   void RecalcData();
   nsChangeHint CalcDifference(const nsStyleMargin& aOther) const;
   static nsChangeHint MaxDifference() {
-    return NS_SubtractHint(NS_STYLE_HINT_REFLOW,
-                           NS_CombineHint(nsChangeHint_ClearDescendantIntrinsics,
-                                          nsChangeHint_NeedDirtyReflow));
+    return NS_CombineHint(nsChangeHint_NeedReflow,
+                          nsChangeHint_ClearAncestorIntrinsics);
   }
   static nsChangeHint MaxDifferenceNeverInherited() {
     // CalcDifference can return both nsChangeHint_ClearAncestorIntrinsics and