Use new is*Element() helper functions in CSS code

Source/core/css/CSSFontFaceSource.cpp

 /*
  * Copyright (C) 2007, 2008, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/css/CSSFontFaceSource.h"
 
 #include "RuntimeEnabledFeatures.h"
 #include "core/css/CSSCustomFontData.h"
 #include "core/css/CSSFontFace.h"
+#include "core/dom/ElementTraversal.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/FontDescription.h"
 #include "platform/fonts/SimpleFontData.h"
 #include "public/platform/Platform.h"
 #include "wtf/CurrentTime.h"
 
 #if ENABLE(SVG_FONTS)
 #include "SVGNames.h"
 #include "core/svg/SVGFontData.h"
 #include "core/svg/SVGFontElement.h"
@@ skipping 126 matching lines @@
                     String fragmentIdentifier;
                     size_t start = m_string.find('#');
                     if (start != kNotFound)
                         fragmentIdentifier = m_string.string().substring(start + 1);
                     m_externalSVGFontElement = m_font->getSVGFontById(fragmentIdentifier);
                 }
 
                 if (!m_externalSVGFontElement)
                     return nullptr;
 
-                SVGFontFaceElement* fontFaceElement = 0;
-
                 // Select first <font-face> child
-                for (Node* fontChild = m_externalSVGFontElement->firstChild(); fontChild; fontChild = fontChild->nextSibling()) {
-                    if (fontChild->hasTagName(SVGNames::font_faceTag)) {
-                        fontFaceElement = toSVGFontFaceElement(fontChild);
-                        break;
-                    }
-                }
-
-                if (fontFaceElement) {
+                if (SVGFontFaceElement* fontFaceElement = Traversal<SVGFontFaceElement>::firstChild(*m_externalSVGFontElement)) {
                     if (!m_svgFontFaceElement) {
                         // We're created using a CSS @font-face rule, that means we're not associated with a SVGFontFaceElement.
                         // Use the imported <font-face> tag as referencing font-face element for these cases.
                         m_svgFontFaceElement = fontFaceElement;
                     }
 
                     fontData = SimpleFontData::create(
                         SVGFontData::create(fontFaceElement),
                         fontDescription.effectiveFontSize(),
                         fontDescription.isSyntheticBold(),
@@ skipping 136 matching lines @@
     if (size < 50 * 1024)
         return "WebFont.DownloadTime.1.10KBTo50KB";
     if (size < 100 * 1024)
         return "WebFont.DownloadTime.2.50KBTo100KB";
     if (size < 1024 * 1024)
         return "WebFont.DownloadTime.3.100KBTo1MB";
     return "WebFont.DownloadTime.4.Over1MB";
 }
 
 }