Rename default -> initial style and use singletons.

Source/core/layout/style/SVGLayoutStyle.h

Index: Source/core/layout/style/SVGLayoutStyle.h
diff --git a/Source/core/layout/style/SVGLayoutStyle.h b/Source/core/layout/style/SVGLayoutStyle.h
index f3710128ea83b020c5dbdf7f32fb1a8faed8c5bf..d38856308af46f0f54e953a5b57c64b65cd3d155 100644
--- a/Source/core/layout/style/SVGLayoutStyle.h
+++ b/Source/core/layout/style/SVGLayoutStyle.h
@@ -447,11 +447,11 @@ protected:
     DataRef<StyleResourceData> resources;
 
 private:
-    enum CreateDefaultType { CreateDefault };
+    enum CreateInitialType { CreateInitial };
 
     SVGLayoutStyle();
     SVGLayoutStyle(const SVGLayoutStyle&);
-    SVGLayoutStyle(CreateDefaultType); // Used to create the default style.
+    SVGLayoutStyle(CreateInitialType); // Used to create the initial style singleton.
 
     bool diffNeedsLayoutAndPaintInvalidation(const SVGLayoutStyle* other) const;
     bool diffNeedsPaintInvalidation(const SVGLayoutStyle* other) const;