Use isSVG*Element() helpers more in SVG code (Part 2)

Source/core/svg/SVGVKernElement.cpp

Index: Source/core/svg/SVGVKernElement.cpp
diff --git a/Source/core/svg/SVGVKernElement.cpp b/Source/core/svg/SVGVKernElement.cpp
index ff60552df306fee29fe3bdadfc19cf04a63d0ff6..b3bdedbfd193fa349e637e1718eb283bdb37662d 100644
--- a/Source/core/svg/SVGVKernElement.cpp
+++ b/Source/core/svg/SVGVKernElement.cpp
@@ -41,8 +41,8 @@ Node::InsertionNotificationRequest SVGVKernElement::insertedInto(ContainerNode*
 {
     if (rootParent->inDocument()) {
         ContainerNode* fontNode = parentNode();
-        if (fontNode && fontNode->hasTagName(SVGNames::fontTag))
-            toSVGFontElement(fontNode)->invalidateGlyphCache();
+        if (isSVGFontElement(fontNode))
+            toSVGFontElement(*fontNode).invalidateGlyphCache();
     }
 
     return SVGElement::insertedInto(rootParent);
@@ -51,8 +51,8 @@ Node::InsertionNotificationRequest SVGVKernElement::insertedInto(ContainerNode*
 void SVGVKernElement::removedFrom(ContainerNode* rootParent)
 {
     ContainerNode* fontNode = parentNode();
-    if (fontNode && fontNode->hasTagName(SVGNames::fontTag))
-        toSVGFontElement(fontNode)->invalidateGlyphCache();
+    if (isSVGFontElement(fontNode))
+        toSVGFontElement(*fontNode).invalidateGlyphCache();
 
     SVGElement::removedFrom(rootParent);
 }