Revert of Support for :enabled selector on Anchor & Area elements (patchset #2 id:20001 of https://codereview.chromium.org/408293002/)

Reason for revert:
HTML spec has been modified [1] to disable support for :enabled CSS selector on Anchor, Area & Link elements, after discussion on W3C Bugzilla [2].

[1] https://html5.org/r/8818
[2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=26622

Original issue's description:
> Support for :enabled selector on Anchor & Area elements
> 
> Updates the PseudoEnabled selector checker to check for Anchor & Area
> elements with a link. Reverts ef7563d
> which removed relevant Shadow DOM tests.
> 
> Spec: http://html.spec.whatwg.org/#selector-enabled
> 
> BUG=393105
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179427

TBR=esprehn@chromium.org,alexis.menard@intel.com,dglazkov@chromium.org,jchaffraix@chromium.org
BUG=393105

Review URL: https://codereview.chromium.org/610683002

git-svn-id: svn://svn.chromium.org/blink/trunk@182932 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Author: brunoabinader

LayoutTests/fast/dom/shadow/pseudoclass-update-enabled-anchor-expected.html

@@ -787,8 +787,6 @@ bool SelectorChecker::checkOne(const SelectorCheckingContext& context, const Sib
         case CSSSelector::PseudoEnabled:
             if (element.isFormControlElement() || isHTMLOptionElement(element) || isHTMLOptGroupElement(element))
                 return !element.isDisabledFormControl();
-            else if (isHTMLAnchorElement(element) || isHTMLAreaElement(element))
-                return element.isLink();
             break;
         case CSSSelector::PseudoFullPageMedia:
             return element.document().isMediaDocument();

LayoutTests/fast/dom/shadow/pseudoclass-update-enabled-anchor.html

@@ -195,8 +195,6 @@ void HTMLAnchorElement::parseAttribute(const QualifiedName& name, const AtomicSt
         if (wasLink || isLink()) {
             pseudoStateChanged(CSSSelector::PseudoLink);
             pseudoStateChanged(CSSSelector::PseudoVisited);
-            if (wasLink != isLink())
-                pseudoStateChanged(CSSSelector::PseudoEnabled);
         }
         if (wasLink && !isLink() && treeScope().adjustedFocusedElement() == this) {
             // We might want to call blur(), but it's dangerous to dispatch