Remove RenderObjectChildList::beforePseudoElementRenderer and afterPseudoElementRenderer
https://bugs.webkit.org/show_bug.cgi?id=106132

Reviewed by Abhishek Arya.

We no longer need the complicated traversals in beforePseudoElementRenderer
and afterPseudoElementRenderer since we can get the renderers of pseudo
elements through the node. This removes all that code and swaps it for
Element::pseudoElementRenderer.

This is possible now that r138850 removed all the now incorrect manual
management of pseudo element renderers from the render tree that was
left over from before the switch to DOM based pseudo elements.

No new tests, just refactoring.

* css/CSSComputedStyleDeclaration.cpp:
(WebCore::CSSComputedStyleDeclaration::getPropertyCSSValue):
* dom/Element.cpp:
(WebCore::Element::pseudoElementRenderer):
    Added, gets the renderer of the pseudo element by PseudoId if it
    exists.
* dom/Element.h:
(Element):
* dom/NodeRenderingTraversal.cpp:
(WebCore::NodeRenderingTraversal::nextSiblingSlow):
(WebCore::NodeRenderingTraversal::previousSiblingSlow):
* rendering/RenderCounter.cpp:
(WebCore::previousInPreOrder):
(WebCore::previousSiblingOrParent):
(WebCore::nextInPreOrder):
* rendering/RenderObject.h:
(WebCore::RenderObject::lastChild):
* rendering/RenderObjectChildList.cpp:
* rendering/RenderObjectChildList.h:
(RenderObjectChildList):
* rendering/RenderTreeAsText.cpp:
(WebCore::counterValueForElement):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138909 268f45cc-cd09-0410-ab3c-d52691b4dbfc