Introduce toSVGAnimateElement(), and use it

Source/core/svg/SVGAnimateElement.h

Index: Source/core/svg/SVGAnimateElement.h
diff --git a/Source/core/svg/SVGAnimateElement.h b/Source/core/svg/SVGAnimateElement.h
index d9873744a7c09e540994213809c696a7780b2616..f53a5bbe10e1740c3af5e82daef1f0c75ef463b3 100644
--- a/Source/core/svg/SVGAnimateElement.h
+++ b/Source/core/svg/SVGAnimateElement.h
@@ -23,6 +23,7 @@
 #ifndef SVGAnimateElement_h
 #define SVGAnimateElement_h
 
+#include "SVGNames.h"
 #include "core/svg/SVGAnimationElement.h"
 #include "wtf/OwnPtr.h"
 
@@ -73,6 +74,16 @@ private:
     OwnPtr<SVGAnimatedTypeAnimator> m_animator;
 };
 
+inline SVGAnimateElement* toSVGAnimateElement(Element* element)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!element
+        || element->hasTagName(SVGNames::animateTag)
+        || element->hasTagName(SVGNames::animateColorTag)
+        || element->hasTagName(SVGNames::animateTransformTag)
+        || element->hasTagName(SVGNames::setTag));
+    return static_cast<SVGAnimateElement*>(element);
+}
+
 } // namespace WebCore
 
 #endif // SVGAnimateElement_h