Reviewed by Andreas Kling.

Node::m_parentOrShadowHostNode is currently used both as the parent pointer for regular nodes and as the host
pointer for ShadowRoots. This is confusing. It is also slow as it introduces a branch to all code paths that 
want to traverse ancestors normally, without leaving the shadow trees. This is much more popular than
traversing through.
        
This patch makes the Node have a pure parent pointer only and adds the host element pointer as a separate
member in ShadowRoot. This eliminates the ShadowRoot test branch from Node::parentNode() as the pointer is
now always null in the root node.
        
ShadowRoot grows by a pointer. This is not significant as there are few ShadowRoots compared to Nodes.

* css/StyleResolver.cpp:
(WebCore::StyleResolver::pushParentShadowRoot):
(WebCore::StyleResolver::popParentShadowRoot):
* dom/Attr.cpp:
(WebCore::Attr::createTextChild):
* dom/ComposedShadowTreeWalker.cpp:
(WebCore::ComposedShadowTreeWalker::traverseParentBackToShadowRootOrHost):
* dom/ContainerNode.cpp:
(WebCore::ContainerNode::insertBeforeCommon):
(WebCore::ContainerNode::removeBetween):
* dom/ContainerNodeAlgorithms.cpp:
(WebCore::ChildNodeInsertionNotifier::notifyDescendantInsertedIntoDocument):
(WebCore::ChildNodeRemovalNotifier::notifyDescendantRemovedFromDocument):
* dom/ContainerNodeAlgorithms.h:
(WebCore::appendChildToContainer):
(WebCore::Private::addChildNodesToDeletionQueue):
* dom/Document.h:
(WebCore::Node::Node):
* dom/Element.cpp:
(WebCore::Element::addShadowRoot):
(WebCore::Element::removeShadowRoot):
* dom/ElementRareData.h:
(WebCore::ElementRareData::releasePseudoElement):
* dom/EventPathWalker.cpp:
(WebCore::EventPathWalker::moveToParent):
* dom/EventRetargeter.cpp:
(WebCore::determineDispatchBehavior):
* dom/EventRetargeter.h:
(WebCore::EventRetargeter::eventTargetRespectingTargetRules):
* dom/Node.cpp:
(WebCore::Node::shadowHost):
(WebCore::Node::deprecatedShadowAncestorNode):
(WebCore::Node::parentOrShadowHostElement):
* dom/Node.h:
(WebCore::Node::hasTreeSharedParent):
        
    Shadow host elements refs the ShadowRoot. There is no reason to use TreeShared to keep it alive.

(WebCore::Node::setParentNode):
(WebCore::Node::parentNode):
(WebCore::Node::parentNodeGuaranteedHostFree):
* dom/PseudoElement.cpp:
(WebCore::PseudoElement::PseudoElement):
* dom/ShadowRoot.cpp:
(WebCore::ShadowRoot::ShadowRoot):
(WebCore::ShadowRoot::setInnerHTML):
(WebCore::ShadowRoot::setApplyAuthorStyles):
(WebCore::ShadowRoot::setResetStyleInheritance):
* dom/ShadowRoot.h:
        
    Rename host() -> hostElement() for clarity.

(WebCore::Node::parentOrShadowHostNode):
* dom/Text.cpp:
(WebCore::isSVGShadowText):
* dom/TreeScope.cpp:
(WebCore::TreeScope::focusedElement):
* html/shadow/ContentDistributor.cpp:
(WebCore::ContentDistributor::ensureDistribution):
* html/shadow/InsertionPoint.cpp:
(WebCore::InsertionPoint::insertedInto):
(WebCore::InsertionPoint::removedFrom):
(WebCore::InsertionPoint::parseAttribute):
* page/DragController.cpp:
(WebCore::asFileInput):
* page/EventHandler.cpp:
(WebCore::EventHandler::handleMousePressEvent):
(WebCore::instanceAssociatedWithShadowTreeElement):
* page/FocusController.cpp:
(WebCore::FocusNavigationScope::owner):
* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::hasLineIfEmpty):
* rendering/RenderLayer.cpp:
(WebCore::rendererForScrollbar):
* svg/SVGElementInstance.h:
(WebCore::SVGElementInstance::setParentNode):
            
    Renamed so it works with appendChildToContainer template.

* svg/SVGStyledElement.cpp:
(WebCore::SVGStyledElement::title):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154165 268f45cc-cd09-0410-ab3c-d52691b4dbfc