SVG: Items inserted into list should be made a tear-off.

Source/core/svg/properties/SVGPropertyTearOff.h

Index: Source/core/svg/properties/SVGPropertyTearOff.h
diff --git a/Source/core/svg/properties/SVGPropertyTearOff.h b/Source/core/svg/properties/SVGPropertyTearOff.h
index caee1657c7733250c7f932545dd139fb8132ce2c..00ee10a7830805a7f5527b99fd36e40c52cf4704 100644
--- a/Source/core/svg/properties/SVGPropertyTearOff.h
+++ b/Source/core/svg/properties/SVGPropertyTearOff.h
@@ -83,6 +83,15 @@ public:
         return m_attributeName;
     }
 
+    void attachToSVGElementAttribute(SVGElement* contextElement, const QualifiedName& attributeName)
+    {
+        ASSERT(!isImmutable());
+        ASSERT(contextElement);
+        ASSERT(attributeName != nullQName());
+        m_contextElement = contextElement;
+        m_attributeName = attributeName;
+    }
+
     virtual AnimatedPropertyType type() const = 0;
 
 protected: