Bug 1169440 patch 5 - Adjust hints in CalcDifference methods to emit new nsChangeHint_ReflowChangesSizeOrPosition hint. r=heycam

Note that most of what is needed was actually taken care of by patch 1's
addition of the new hint to nsChangeHint_AllReflowHints.

layout/style/nsStyleStruct.cpp

@@ -333,8 +333,9 @@ nsChangeHint nsStyleMargin::CalcDifference(const nsStyleMargin& aOther) const
   }
   // Margin differences can't affect descendant intrinsic sizes and
   // don't need to force children to reflow.
-  return NS_CombineHint(nsChangeHint_NeedReflow,
-                        nsChangeHint_ClearAncestorIntrinsics);
+  return nsChangeHint_NeedReflow |
+         nsChangeHint_ReflowChangesSizeOrPosition |
+         nsChangeHint_ClearAncestorIntrinsics;
 }
 
 nsStylePadding::nsStylePadding()

layout/style/nsStyleStruct.h

@@ -609,12 +609,13 @@ struct nsStyleMargin {
   void RecalcData();
   nsChangeHint CalcDifference(const nsStyleMargin& aOther) const;
   static nsChangeHint MaxDifference() {
-    return NS_CombineHint(nsChangeHint_NeedReflow,
-                          nsChangeHint_ClearAncestorIntrinsics);
+    return nsChangeHint_NeedReflow |
+           nsChangeHint_ReflowChangesSizeOrPosition |
+           nsChangeHint_ClearAncestorIntrinsics;
   }
   static nsChangeHint DifferenceAlwaysHandledForDescendants() {
-    // CalcDifference can return both nsChangeHint_ClearAncestorIntrinsics and
-    // nsChangeHint_NeedReflow as hints not handled for descendants.
+    // CalcDifference can return all of the reflow hints sometimes not
+    // handled for descendants as hints not handled for descendants.
     return nsChangeHint(0);
   }