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

Source/core/svg/SVGLinearGradientElement.h

Index: Source/core/svg/SVGLinearGradientElement.h
diff --git a/Source/core/svg/SVGLinearGradientElement.h b/Source/core/svg/SVGLinearGradientElement.h
index 179424e1ca74320d243f39e6c587090dcf86a5c4..c0b61fc4a1fe63a4a07cea26b12d449f7cb69eba 100644
--- a/Source/core/svg/SVGLinearGradientElement.h
+++ b/Source/core/svg/SVGLinearGradientElement.h
@@ -35,6 +35,11 @@ public:
 
     bool collectGradientAttributes(LinearGradientAttributes&);
 
+    SVGAnimatedLength* x1() const { return m_x1.get(); }
+    SVGAnimatedLength* y1() const { return m_y1.get(); }
+    SVGAnimatedLength* x2() const { return m_x2.get(); }
+    SVGAnimatedLength* y2() const { return m_y2.get(); }
+
 private:
     explicit SVGLinearGradientElement(Document&);
 
@@ -46,11 +51,11 @@ private:
 
     virtual bool selfHasRelativeLengths() const;
 
+    RefPtr<SVGAnimatedLength> m_x1;
+    RefPtr<SVGAnimatedLength> m_y1;
+    RefPtr<SVGAnimatedLength> m_x2;
+    RefPtr<SVGAnimatedLength> m_y2;
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGLinearGradientElement)
-        DECLARE_ANIMATED_LENGTH(X1, x1)
-        DECLARE_ANIMATED_LENGTH(Y1, y1)
-        DECLARE_ANIMATED_LENGTH(X2, x2)
-        DECLARE_ANIMATED_LENGTH(Y2, y2)
     END_DECLARE_ANIMATED_PROPERTIES
 };