Use AtomicString API directly

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 0fd3afda060dfafada8120b6a5f40f4d401e331c..e108167657bf8b815f3951ec517a58b518d0552c 100644
--- a/Source/core/svg/SVGVKernElement.cpp
+++ b/Source/core/svg/SVGVKernElement.cpp
@@ -67,7 +67,7 @@ void SVGVKernElement::buildVerticalKerningPair(KerningPairVector& kerningPairs)
         && parseGlyphName(g2, kerningPair.glyphName2)
         && parseKerningUnicodeString(u1, kerningPair.unicodeRange1, kerningPair.unicodeName1)
         && parseKerningUnicodeString(u2, kerningPair.unicodeRange2, kerningPair.unicodeName2)) {
-        kerningPair.kerning = fastGetAttribute(SVGNames::kAttr).string().toFloat();
+        kerningPair.kerning = fastGetAttribute(SVGNames::kAttr).toFloat();
         kerningPairs.append(kerningPair);
     }
 }