Reset SVGAnimationElement values animation state on attribute changes

Source/core/svg/SVGAnimationElement.cpp

Index: Source/core/svg/SVGAnimationElement.cpp
diff --git a/Source/core/svg/SVGAnimationElement.cpp b/Source/core/svg/SVGAnimationElement.cpp
index f17bd5e7bd58545e0faea0e193c211344fdbf562..bc18e7eed4b08b41527ef9523d24ae119f370f96 100644
--- a/Source/core/svg/SVGAnimationElement.cpp
+++ b/Source/core/svg/SVGAnimationElement.cpp
@@ -242,6 +242,8 @@ void SVGAnimationElement::animationAttributeChanged()
 {
     // Assumptions may not hold after an attribute change.
     m_animationValid = false;
+    m_lastValuesAnimationFrom = String();
+    m_lastValuesAnimationTo = String();
     setInactive();
 }