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

Source/core/svg/SVGGlyphElement.h

Index: Source/core/svg/SVGGlyphElement.h
diff --git a/Source/core/svg/SVGGlyphElement.h b/Source/core/svg/SVGGlyphElement.h
index 437676e1377f2d3b7e5b4f53c5988cbf8aff8fcb..90772d738f65b9d4ee733e334872bf7227f2d0fa 100644
--- a/Source/core/svg/SVGGlyphElement.h
+++ b/Source/core/svg/SVGGlyphElement.h
@@ -23,6 +23,7 @@
 #define SVGGlyphElement_h
 
 #if ENABLE(SVG_FONTS)
+#include "SVGNames.h"
 #include "core/platform/graphics/SVGGlyph.h"
 #include "core/svg/SVGElement.h"
 
@@ -57,6 +58,12 @@ private:
     void invalidateGlyphCache();
 };
 
+inline SVGGlyphElement* toSVGGlyphElement(Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::glyphTag));
+    return static_cast<SVGGlyphElement*>(node);
+}
+
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)