2009-12-17 Yaar Schnitman <yaar@chromium.org>

      Reviewed by Darin Fisher.

        Added WebPageSerializer to WebKit API and enriched the WebNode hierarchy to support
        downstream unit-testing of serialization.

        WebPageSerializer was adapted from Chromium's dom_serializer, originally authored by Johnny Ding.

        https://bugs.webkit.org/show_bug.cgi?id=31737

        * WebKit.gyp:
        * public/WebDocument.h: Added.
        (WebKit::WebDocument::WebDocument):
        (WebKit::WebDocument::operator=):
        (WebKit::WebDocument::assign):
        * public/WebElement.h:
        * public/WebFormElement.h:
        (WebKit::WebFormElement::operator=):
        * public/WebFrame.h:
        * public/WebNode.h:
        (WebKit::WebNode::):
        (WebKit::WebNode::toConstElement):
        * public/WebNodeCollection.h: Added.
        (WebKit::WebNodeCollection::~WebNodeCollection):
        (WebKit::WebNodeCollection::WebNodeCollection):
        (WebKit::WebNodeCollection::operator=):
        * public/WebNodeList.h: Added.
        (WebKit::WebNodeList::~WebNodeList):
        (WebKit::WebNodeList::WebNodeList):
        (WebKit::WebNodeList::operator=):
        * public/WebPageSerializer.h: Added.
        * public/WebPageSerializerClient.h: Added.
        (WebKit::WebPageSerializerClient::):
        (WebKit::WebPageSerializerClient::WebPageSerializerClient):
        (WebKit::WebPageSerializerClient::~WebPageSerializerClient):
        * public/WebString.h:
        * public/WebView.h:
        * src/AssertMatchingEnums.cpp:
        * src/DOMUtilitiesPrivate.cpp:
        (WebKit::elementHasLegalLinkAttribute):
        * src/DOMUtilitiesPrivate.h:
        * src/WebDocument.cpp: Added.
        (WebKit::WebDocument::WebDocument):
        (WebKit::WebDocument::operator=):
        (WebKit::WebDocument::operator WTF::PassRefPtr<Document>):
        (WebKit::WebDocument::frame):
        (WebKit::WebDocument::isHTMLDocument):
        (WebKit::WebDocument::baseU