Use the new is<>() / downcast<>() for Attr Nodes
https://bugs.webkit.org/show_bug.cgi?id=137183

Reviewed by Ryosuke Niwa.

Use the new is<>() / downcast<>() for Attr Nodes instead of isAttr() /
toAttr().

No new tests, no behavior change.

* dom/Attr.h:
(WebCore::isAttr):
* dom/Document.cpp:
(WebCore::Document::importNode):
(WebCore::Document::adoptNode):
* dom/NamedNodeMap.cpp:
(WebCore::NamedNodeMap::setNamedItem):
* dom/Node.cpp:
(WebCore::Node::compareDocumentPosition):
* inspector/InspectorDOMAgent.cpp:
(WebCore::InspectorDOMAgent::buildObjectForNode):
* inspector/InspectorNodeFinder.cpp:
(WebCore::InspectorNodeFinder::searchUsingXPath):
* xml/XPathNodeSet.cpp:
(WebCore::XPath::sortBlock):
(WebCore::XPath::NodeSet::sort):
(WebCore::XPath::findRootNode):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@174038 268f45cc-cd09-0410-ab3c-d52691b4dbfc