[SVG] SVGLength{,List} migration to new SVG property impl.

Source/core/svg/SVGMaskElement.h

Index: Source/core/svg/SVGMaskElement.h
diff --git a/Source/core/svg/SVGMaskElement.h b/Source/core/svg/SVGMaskElement.h
index a4b09ae2e3aa32fbe0c2e2ba6c2853bef4a4313a..97bd2b65d3173e7081fdc83367fb56d98b36951a 100644
--- a/Source/core/svg/SVGMaskElement.h
+++ b/Source/core/svg/SVGMaskElement.h
@@ -37,6 +37,11 @@ class SVGMaskElement FINAL : public SVGElement,
 public:
     static PassRefPtr<SVGMaskElement> create(Document&);
 
+    SVGAnimatedLength* x() const { return m_x.get(); }
+    SVGAnimatedLength* y() const { return m_y.get(); }
+    SVGAnimatedLength* width() const { return m_width.get(); }
+    SVGAnimatedLength* height() const { return m_height.get(); }
+
 private:
     explicit SVGMaskElement(Document&);
 
@@ -52,13 +57,13 @@ private:
 
     virtual bool selfHasRelativeLengths() const;
 
+    RefPtr<SVGAnimatedLength> m_x;
+    RefPtr<SVGAnimatedLength> m_y;
+    RefPtr<SVGAnimatedLength> m_width;
+    RefPtr<SVGAnimatedLength> m_height;
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGMaskElement)
         DECLARE_ANIMATED_ENUMERATION(MaskUnits, maskUnits, SVGUnitTypes::SVGUnitType)
         DECLARE_ANIMATED_ENUMERATION(MaskContentUnits, maskContentUnits, SVGUnitTypes::SVGUnitType)
-        DECLARE_ANIMATED_LENGTH(X, x)
-        DECLARE_ANIMATED_LENGTH(Y, y)
-        DECLARE_ANIMATED_LENGTH(Width, width)
-        DECLARE_ANIMATED_LENGTH(Height, height)
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES