Remove WebPageSerialzier related code.

sky/engine/core/dom/Element.cpp

Index: sky/engine/core/dom/Element.cpp
diff --git a/sky/engine/core/dom/Element.cpp b/sky/engine/core/dom/Element.cpp
index 5ecf31db86869018bb1049dca79fd1f097265770..7ed41225758bf351df7cc1b287dccd6d15d878d8 100644
--- a/sky/engine/core/dom/Element.cpp
+++ b/sky/engine/core/dom/Element.cpp
@@ -660,16 +660,6 @@ void Element::attributeChanged(const QualifiedName& name, const AtomicString& ne
         setNeedsStyleRecalc(SubtreeStyleChange);
 }
 
-bool Element::hasLegalLinkAttribute(const QualifiedName&) const
-{
-    return false;
-}
-
-const QualifiedName& Element::subResourceAttributeName() const
-{
-    return nullName;
-}
-
 inline void Element::attributeChangedFromParserOrByCloning(const QualifiedName& name, const AtomicString& newValue, AttributeModificationReason reason)
 {
     if (name == HTMLNames::isAttr)