Reviewed by Maciej.

        - https://bugs.webkit.org/show_bug.cgi?id=19239

        Removed code that would only useful if if there was any way to create an Entity
        node or if we populated EntityReference nodes. It's likely that we'll remove
        these node types entirely in some future version of WebKit, depending in part
        on what happens with these in HTML 5.

        1.8% speedup of Acid3 test 26.

        The only read-only nodes we ever create are EntityReference nodes.
        These are only created by explicit calls to the Document.createEntityReference
        function. Since the created nodes are read-only, there can be no children of
        these nodes, so no other types of nodes can be read-only despite the rule that
        makes descendants of Entity and EntityReference nodes read-only.

        * bindings/objc/DOM.mm: Removed unneeded include.

        * dom/Attr.cpp:
        (WebCore::Attr::setValue): Removed unnecessary isReadOnlyNode check.
        (WebCore::Attr::setNodeValue): Ditto.
        * dom/CharacterData.cpp:
        (WebCore::CharacterData::setData): Removed unnecessary isReadOnlyNode check.
        (WebCore::CharacterData::substringData): Don't initialize the ec variable before
        calling checkCharDataOperation, since that function already does it.
        (WebCore::CharacterData::appendData): Removed unnecessary isReadOnlyNode check.
        (WebCore::CharacterData::insertData): Don't initialize ec.
        (WebCore::CharacterData::deleteData): Ditto.
        (WebCore::CharacterData::replaceData): Ditto.
        (WebCore::CharacterData::setNodeValue): Removed now-misleading comment.
        (WebCore::CharacterData::checkCharDataOperation): Removed unnecessary
        isReadOnlyNode check.
        * dom/CharacterData.h: Made checkCharDataOperation private and non-virtual
        since it's never used or defined in any other class.

        * dom/Element.cpp:
        (WebCore::Element::setAttribute): Removed unneeded isReadOnlyNode check.

        * dom/Entity.cpp: Removed the entire contents of this file.

        * dom/Entity.h: Replaced the class with a stub -- just enough to keep the
        public bindings (JavaScript and Objective-C compiling), but the class is
        abstract and can't be instantianted.

        * dom/EntityReference.cpp: Removed unused constructor.
        (WebCore::EntityReference::cloneNode): Removed unneeded code and comments
        to clone nonexistent child nodes.
        * dom/EntityReference.h: Removed unused constructor and unnecessary override
        of childTypeAllowed, since no children are allowed at all.

        * dom/NamedAttrMap.cpp:
        (WebCore::NamedAttrMap::setNamedItem): Removed unneeded isReadOnlyNode check.
        (WebCore::NamedAttrMap::removeNamedItem): Ditto.
        * dom/NamedAttrMap.h: Removed isReadOnlyNode function.

        * dom/Node.cpp: Removed the old isReadOnlyNode function. It made lots of
        virtual nodeType function calls.
        * dom/Node.h:
        (WebCore::Node::isReadOnlyNode): Replaced the old virtual isReadOnlyNode
        function with a new simple non-virtual one.

        * dom/ProcessingInstruction.cpp:
        (WebCore::ProcessingInstruction::setData): Removed unneeded isReadOnlyNode
        check.

        * dom/Text.cpp:
        (WebCore::Text::splitText): Removed unneeded isReadOnlyNode check.
        (WebCore::Text::replaceWholeText): Removed unnecessary isReadOnlyNode assertion.
        There is no reason for this function to go out of its way to mention the
        read-only node issue when none of the other DOM mutation functions do.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@34138 268f45cc-cd09-0410-ab3c-d52691b4dbfc