Update :active definition to not consider disabledness

This matches Gecko and WebKit. The disabled condition was added to the spec in 9985973 but not implemented uniformly. As discussed in #6635, it doesn't work very well and is inconsistent with other similar pseudo-classes, like :hover.

This also removes the consideration of <link> elements with href="" attributes, since they no longer have activation behavior as of 1e0ee7f. And it updates the definitions of both :active and :hover to be based on the latest Selectors spec, which notably includes the ancestor condition over the flat tree at the CSS layer, instead of having HTML handle that.

There remains some lack of interop around elements such as <input type=radio> which have activation behavior but are not on the list of elements for which "in a formal activation state" is considered. #6635 stays open to track that case.

source

@@ -70318,58 +70318,40 @@ contradict people?
    <dt><dfn selector noexport><code data-x="selector-active">:active</code></dfn></dt>
    <dd>
     <p>The <code data-x="selector-active">:active</code> <span>pseudo-class</span> is defined to
-    match an element
-    <q cite="https://drafts.csswg.org/selectors3/#the-user-action-pseudo-classes-hover-act">while an
-    element is <dfn><i data-x="concept-selector-active">being activated</i></dfn> by the user</q>.</p>
+    match an element <q cite="https://drafts.csswg.org/selectors/#the-active-pseudo">while an
+    element is <dfn><i data-x="concept-selector-active">being activated</i></dfn> by the
+    user</q>.</p>
 
     <p>To determine whether a particular element is <i data-x="concept-selector-active">being activated</i> for the purposes of
     defining the <code data-x="selector-active">:active</code> <span>pseudo-class</span> only, an
     HTML user agent must use the first relevant entry in the following list.</p>
 
     <dl>
-     <dt>If the element has a descendant that is currently matching the <code
-     data-x="selector-active">:active</code> <span>pseudo-class</span></dt>
-     <dd><p>The element is <i data-x="concept-selector-active">being activated</i>.</p></dd>
-
-     <!-- this even trumps the <button disabled> stuff below:
-            https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=3355
-            https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=3356
-       -->
-
      <dt>If the element is the <span>labeled control</span> of a <code>label</code> element that is
      currently matching <code data-x="selector-active">:active</code></dt>
      <dd><p>The element is <i data-x="concept-selector-active">being activated</i>.</p></dd>
 
-     <!-- this even trumps the <button disabled> stuff below:
-            https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=3354
-       -->
-
      <dt>If the element is a <code>button</code> element</dt>
      <dt>If the element is an <code>input</code> element whose <code
      data-x="attr-input-type">type</code> attribute is in the <span
      data-x="attr-input-type-submit">Submit Button</span>, <span
      data-x="attr-input-type-image">Image Button</span>, <span data-x="attr-input-type-reset">Reset
      Button</span>, or <span data-x="attr-input-type-button">Button</span> state</dt>
+     <dt>If the element is an <code>a</code> element that has an <code
+     data-x="attr-hyperlink-href">href</code> attribute</dt>
+     <dt>If the element is an <code>area</code> element that has an <code
+     data-x="attr-hyperlink-href">href</code> attribute</dt>
+     <dt>If the element is <span>focusable</span></dt>
      <dd>
-      <p>The element is <i data-x="concept-selector-active">being activated</i> if it is <span>in a formal activation state</span>
-      and it is not <span data-x="concept-fe-disabled">disabled</span>.</p>
+      <p>The element is <i data-x="concept-selector-active">being activated</i> if it is <span>in a
+      formal activation state</span>.</p>
 
       <p class="example">For example, if the user is using a keyboard to push a <code>button</code>
       element by pressing the space bar, the element would match this <span>pseudo-class</span> in
       between the time that the element received the <code data-x="event-keydown">keydown</code>
       event and the time the element received the <code data-x="event-keyup">keyup</code> event.</p>
      </dd>
 
-     <dt>If the element is an <code>a</code> element that has an <code
-     data-x="attr-hyperlink-href">href</code> attribute</dt>
-     <dt>If the element is an <code>area</code> element that has an <code
-     data-x="attr-hyperlink-href">href</code> attribute</dt>
-     <dt>If the element is a <code>link</code> element that has an <code
-     data-x="attr-link-href">href</code> attribute</dt>
-     <dt>If the element is <span>focusable</span></dt>
-     <dd><p>The element is <i data-x="concept-selector-active">being activated</i> if it is <span>in a formal activation
-     state</span>.</p></dd>
-
      <dt>If the element is <span>being actively pointed at</span></dt>
      <dd><p>The element is <i data-x="concept-selector-active">being activated</i>.</p></dd>
     </dl>
@@ -70384,31 +70366,36 @@ contradict people?
     element using a pointing device while that pointing device is in the "down" state (e.g. for a
     mouse, between the time the mouse button is pressed and the time it is depressed; for a finger
     in a multitouch environment, while the finger is touching the display surface).</p>
+
+    <p class="note">Per the definition in <cite>Selectors</cite>, <code
+    data-x="selector-active">:active</code> also matches <span>flat tree</span> ancestors of
+    elements that are <i data-x="concept-selector-active">being activated</i>. <ref
+    spec=SELECTORS></p>
    </dd>
 
    <dt><dfn selector noexport><code data-x="selector-hover">:hover</code></dfn></dt>
    <dd>
-    <p>The <code data-x="selector-hover">:hover</code> <span>pseudo-class</span> is defined to match
-    an element <q
-    cite="https://drafts.csswg.org/selectors3/#the-user-action-pseudo-classes-hover-act">while the
-    user <i>designates</i> an element with a pointing device</q>. For the purposes of defining the
-    <code data-x="selector-hover">:hover</code> <span>pseudo-class</span> only, an HTML user agent
-    must consider an element as being one that the user <i>designates</i> if it is:</p>
+    <p>The <code data-x="selector-hover">:hover</code> <span>pseudo-class</span> is defined to
+    match an element <q cite="https://drafts.csswg.org/selectors/#the-hover-pseudo">while the user
+    <dfn><i data-x="concept-selector-hover">designates</i></dfn> an element with a pointing
+    device</q>. For the purposes of defining the <code data-x="selector-hover">:hover</code>
+    <span>pseudo-class</span> only, an HTML user agent must consider an element as being one that
+    the user <i data-x="concept-selector-hover">designates</i> if it is:</p>
 
     <ul>
      <li>
       <p>An element that the user indicates using a pointing device.</p>
      </li>
 
-     <li>
-      <p>An element that has a descendant that the user indicates using a pointing device.</p>
-     </li>
-
      <li>
       <p>An element that is the <span>labeled control</span> of a <code>label</code> element that is
       currently matching <code data-x="selector-hover">:hover</code>.</p>
      </li>
     </ul>
+
+    <p class="note">Per the definition in <cite>Selectors</cite>, <code
+    data-x="selector-hover">:hover</code> also matches <span>flat tree</span> ancestors of elements
+    that are <i data-x="concept-selector-hover">designated</i>. <ref spec=SELECTORS></p>
 <!--
 Demos:
  https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=1315