Introduce toSVGGlyphElement(), toSVGHKernElement() and toSVGVKernElement(), and use them

Source/core/svg/SVGVKernElement.h

Index: Source/core/svg/SVGVKernElement.h
diff --git a/Source/core/svg/SVGVKernElement.h b/Source/core/svg/SVGVKernElement.h
index e605c7b4b1fcb0ce6ec897e61f10dea25e8f38c3..18f509ff6bce38c8ed944ffe46a0c763f113a8ea 100644
--- a/Source/core/svg/SVGVKernElement.h
+++ b/Source/core/svg/SVGVKernElement.h
@@ -21,6 +21,7 @@
 #define SVGVKernElement_h
 
 #if ENABLE(SVG_FONTS)
+#include "SVGNames.h"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGFontElement.h"
 
@@ -41,6 +42,12 @@ private:
     virtual bool rendererIsNeeded(const NodeRenderingContext&) { return false; }
 };
 
+inline SVGVKernElement* toSVGVKernElement(Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::vkernTag));
+    return static_cast<SVGVKernElement*>(node);
+}
+
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)