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

Source/core/svg/properties/NewSVGAnimatedProperty.cpp

Index: Source/core/svg/properties/NewSVGAnimatedProperty.cpp
diff --git a/Source/core/svg/properties/NewSVGAnimatedProperty.cpp b/Source/core/svg/properties/NewSVGAnimatedProperty.cpp
index 2ec8cc7a278fc5d3e60cf04d232a0041053b23a9..27f43af79d57b4e2b49e898654e7ff5f5494d2d1 100644
--- a/Source/core/svg/properties/NewSVGAnimatedProperty.cpp
+++ b/Source/core/svg/properties/NewSVGAnimatedProperty.cpp
@@ -35,12 +35,20 @@
 
 namespace WebCore {
 
+NewSVGAnimatedPropertyBase::NewSVGAnimatedPropertyBase(SVGElement* contextElement, const QualifiedName& attributeName)
+    : m_contextElement(contextElement)
+    , m_attributeName(attributeName)
+{
+    contextElement->setContextElement();
+}
+
 NewSVGAnimatedPropertyBase::~NewSVGAnimatedPropertyBase()
 {
 }
 
 void NewSVGAnimatedPropertyBase::synchronizeAttribute()
 {
+    ASSERT(needsSynchronizeAttribute());
     AtomicString value(currentValueBase()->valueAsString());
     m_contextElement->setSynchronizedLazyAttribute(m_attributeName, value);
 }