Reviewed by John.

    Reviewed by John.

        - fixed <rdar://problem/4097849> REGRESSION (162-163): importNode creates non-HTML elements, thus style attributes (and some others) don't work

        * khtml/xml/dom_docimpl.h: Add virtual functions HTMLElementNamespace and isHTMLNamespace.
        * khtml/xml/dom_docimpl.cpp:
        (DocumentImpl::importNode): Rearranged this function and fixed the following problems: 1) made sure to ref node while attributes are
        being set on it so it doesn't get destroyed; 2) fixed code to get namespace from the element we are importing to use the IDs from
        the source document, not the destination document; 3) removed unneeded getDocument() call which just returns this; 4) fixed error
        handling for cases where an exception happens while processing the children.
        (DocumentImpl::HTMLElementNamespace): Added. Returns XHTML_NAMESPACE.
        (DocumentImpl::isHTMLNamespace): Added. Returns true for any namespace that matches XHTML_NAMESPACE (case insensitive).
        (DocumentImpl::createElementNS): Changed to call isHTMLNamespace, which will cause it to accept the null namespace in an HTML document.
        This is the change that fixes the bug. Also fixed the code path to do a little less wasteful work in the non-XHTML case.
        (DocumentImpl::createHTMLElement): Pass in HTMLElementNamespace() rather than 0 to tagId.
        (DocumentImpl::attrId): Use isHTMLNamespace instead of allowing the null namespace explicitly.
        (DocumentImpl::tagId): Ditto.

        * khtml/html/html_documentimpl.h: Add overrides for HTMLElementNamespace and isHTMLNamespace.
        * khtml/html/html_documentimpl.cpp:
        (HTMLDocumentImpl::HTMLElementNamespace): Added. Returns 0 so we use the null string for HTML elements inside HTML documents (as before).
        (HTMLDocumentImpl::isHTMLNamespace): Added. Allows 0, and then calls base class to check for the actual XHTML namespace. Thus, we allow
        both no namespace at all and the XHTML namespace inside HTML documents.

        * khtml/html/html_elementimpl.cpp: (HTMLElementImpl::namespaceURI): Changed to call HTMLElementNamespace rather than checking
        isHTMLDocument. Same result as before, but better division of responsibilities.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@9046 268f45cc-cd09-0410-ab3c-d52691b4dbfc