Add font support to PageSerializer

Source/core/css/CSSValue.h

Index: Source/core/css/CSSValue.h
diff --git a/Source/core/css/CSSValue.h b/Source/core/css/CSSValue.h
index 27f6467da15115d99fbacf5ec27af5c0f98b823b..a92bc86a5b532c845ed46447042e49ce06f66424 100644
--- a/Source/core/css/CSSValue.h
+++ b/Source/core/css/CSSValue.h
@@ -74,6 +74,7 @@ public:
     bool isCursorImageValue() const { return m_classType == CursorImageClass; }
     bool isFontFeatureValue() const { return m_classType == FontFeatureClass; }
     bool isFontValue() const { return m_classType == FontClass; }
+    bool isFontFaceSrcValue() const { return m_classType == FontFaceSrcClass; }
     bool isFunctionValue() const { return m_classType == FunctionClass; }
     bool isImageGeneratorValue() const { return m_classType >= CanvasClass && m_classType <= RadialGradientClass; }
     bool isGradientValue() const { return m_classType >= LinearGradientClass && m_classType <= RadialGradientClass; }