Introduce toSVGPatternElement(), use it

Source/core/svg/SVGPatternElement.h

Index: Source/core/svg/SVGPatternElement.h
diff --git a/Source/core/svg/SVGPatternElement.h b/Source/core/svg/SVGPatternElement.h
index b8138176d1c76c396858ea7365e777e1d90804c6..8d091685dc5dd4d46d381ec95cb269b177152181 100644
--- a/Source/core/svg/SVGPatternElement.h
+++ b/Source/core/svg/SVGPatternElement.h
@@ -21,6 +21,7 @@
 #ifndef SVGPatternElement_h
 #define SVGPatternElement_h
 
+#include "SVGNames.h"
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGAnimatedEnumeration.h"
 #include "core/svg/SVGAnimatedLength.h"
@@ -85,6 +86,12 @@ private:
     virtual void synchronizeSystemLanguage() { SVGTests::synchronizeSystemLanguage(this); }
 };
 
+inline SVGPatternElement* toSVGPatternElement(Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::patternTag));
+    return static_cast<SVGPatternElement*>(node);
+}
+
 } // namespace WebCore
 
 #endif