Add font support to PageSerializer

Source/core/css/CSSFontFaceRule.h

Index: Source/core/css/CSSFontFaceRule.h
diff --git a/Source/core/css/CSSFontFaceRule.h b/Source/core/css/CSSFontFaceRule.h
index a042e8fee4154280f5be72a23bb0bbaf894101af..1be5c3a721cb92b0772786e7e2f4b76e100058e4 100644
--- a/Source/core/css/CSSFontFaceRule.h
+++ b/Source/core/css/CSSFontFaceRule.h
@@ -42,6 +42,8 @@ public:
 
     CSSStyleDeclaration* style() const;
 
+    StyleRuleFontFace* styleRule() const { return m_fontFaceRule.get(); }
+
 private:
     CSSFontFaceRule(StyleRuleFontFace*, CSSStyleSheet* parent);
 
@@ -49,6 +51,12 @@ private:
     mutable RefPtr<StyleRuleCSSStyleDeclaration> m_propertiesCSSOMWrapper;
 };
 
+inline CSSFontFaceRule* toCSSFontFaceRule(CSSRule* rule)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(rule->type() == CSSRule::FONT_FACE_RULE);
+    return static_cast<CSSFontFaceRule*>(rule);
+}
+
 } // namespace WebCore
 
 #endif // CSSFontFaceRule_h