Separate repaint and layout requirements of StyleDifference (Step 1)

Source/core/rendering/style/RenderStyleConstants.h

Index: Source/core/rendering/style/RenderStyleConstants.h
diff --git a/Source/core/rendering/style/RenderStyleConstants.h b/Source/core/rendering/style/RenderStyleConstants.h
index 547ce8dba57d291d1a9ebb1772ce7ad380fd4460..47709733e017bb9f09378ee92a15bd4c76860a28 100644
--- a/Source/core/rendering/style/RenderStyleConstants.h
+++ b/Source/core/rendering/style/RenderStyleConstants.h
@@ -44,6 +44,7 @@ enum PrintColorAdjust {
     PrintColorAdjustExact
 };
 
+// FIXME: To be replaced by StyleDifference defined in StyleDifference.h.
 // The difference between two styles.  The following values are used:
 // - StyleDifferenceEqual - The two styles are identical.
 //   FIXME: When style difference is context sensitive, RenderStyle::visualInvalidationDiff() may return
@@ -53,7 +54,7 @@ enum PrintColorAdjust {
 // - StyleDifferenceRepaintLayer - The layer and its descendant layers need to be repainted.
 // - StyleDifferenceLayoutPositionedMovementOnly - Only the position of this positioned object has been updated.
 // - StyleDifferenceLayout - A full layout is required.
-enum StyleDifference {
+enum StyleDifferenceLegacy {
     StyleDifferenceEqual,
     StyleDifferenceRecompositeLayer,
     StyleDifferenceRepaint,