Resolves #978, add back ARIA element reflection IDL (#1755)

Now that HTML spec defines reflection for Element and FrozenArray<Element> attributes (see whatwg/html#7934), we can add back these attributes to ARIA IDL. This is simply a revert of #1260.

Author: mrego

index.html

@@ -13612,7 +13612,7 @@ <h2>Interface Mixin <dfn>ARIAMixin</dfn></h2>
 <pre class="idl">
 interface mixin ARIAMixin {
 attribute DOMString? role;
-<!-- attribute Element? ariaActiveDescendantElement; -->
+attribute Element? ariaActiveDescendantElement;
 attribute DOMString? ariaAtomic;
 attribute DOMString? ariaAutoComplete;
 attribute DOMString? ariaBusy;
@@ -13621,28 +13621,28 @@ <h2>Interface Mixin <dfn>ARIAMixin</dfn></h2>
 attribute DOMString? ariaColIndex;
 attribute DOMString? ariaColIndexText;
 attribute DOMString? ariaColSpan;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaControlsElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaControlsElements;
 attribute DOMString? ariaCurrent;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaDescribedByElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaDescribedByElements;
 attribute DOMString? ariaDescription;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaDetailsElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaDetailsElements;
 attribute DOMString? ariaDisabled;
-<!-- attribute Element? ariaErrorMessageElement; -->
+attribute Element? ariaErrorMessageElement;
 attribute DOMString? ariaExpanded;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaFlowToElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaFlowToElements;
 attribute DOMString? ariaHasPopup;
 attribute DOMString? ariaHidden;
 attribute DOMString? ariaInvalid;
 attribute DOMString? ariaKeyShortcuts;
 attribute DOMString? ariaLabel;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaLabelledByElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaLabelledByElements;
 attribute DOMString? ariaLevel;
 attribute DOMString? ariaLive;
 attribute DOMString? ariaModal;
 attribute DOMString? ariaMultiLine;
 attribute DOMString? ariaMultiSelectable;
 attribute DOMString? ariaOrientation;
-<!-- attribute FrozenArray&lt;Element&gt;? ariaOwnsElements; -->
+attribute FrozenArray&lt;Element&gt;? ariaOwnsElements;
 attribute DOMString? ariaPlaceholder;
 attribute DOMString? ariaPosInSet;
 attribute DOMString? ariaPressed;
@@ -13697,7 +13697,7 @@ <h2>ARIA Attribute Correspondence</h2>
 <table>
 <tr><th>IDL Attribute</th><th>Reflected ARIA Content Attribute</th></tr>
 <tr><td>role</td><td><a href="#introroles">role</a></td></tr>
-<!-- <tr><td><dfn>ariaActiveDescendantElement</dfn></td><td><pref>aria-activedescendant</pref></td></tr> -->
+<tr><td><dfn>ariaActiveDescendantElement</dfn></td><td><pref>aria-activedescendant</pref></td></tr>
 <tr><td><dfn>ariaAtomic</dfn></td><td><pref>aria-atomic</pref></td></tr>
 <tr><td><dfn>ariaAutoComplete</dfn></td><td><pref>aria-autocomplete</pref></td></tr>
 <tr><td><dfn>ariaBusy</dfn></td><td><sref>aria-busy</sref></td></tr>
@@ -13706,28 +13706,28 @@ <h2>ARIA Attribute Correspondence</h2>
 <tr><td><dfn>ariaColIndex</dfn></td><td><pref>aria-colindex</pref></td></tr>
 <tr><td><dfn>ariaColIndexText</dfn></td><td><pref>aria-colindextext</pref></td></tr>
 <tr><td><dfn>ariaColSpan</dfn></td><td><pref>aria-colspan</pref></td></tr>
-<!-- <tr><td><dfn>ariaControlsElements</dfn></td><td><pref>aria-controls</pref></td></tr> -->
+<tr><td><dfn>ariaControlsElements</dfn></td><td><pref>aria-controls</pref></td></tr>
 <tr><td><dfn>ariaCurrent</dfn></td><td><sref>aria-current</sref></td></tr>
-<!-- <tr><td><dfn>ariaDescribedByElements</dfn></td><td><pref>aria-describedby</pref></td></tr> -->
+<tr><td><dfn>ariaDescribedByElements</dfn></td><td><pref>aria-describedby</pref></td></tr>
 <tr><td><dfn>ariaDescription</dfn></td><td><pref>aria-description</pref></td></tr>
-<!-- <tr><td><dfn>ariaDetailsElements</dfn></td><td><pref>aria-details</pref></td></tr> -->
+<tr><td><dfn>ariaDetailsElements</dfn></td><td><pref>aria-details</pref></td></tr>
 <tr><td><dfn>ariaDisabled</dfn></td><td><sref>aria-disabled</sref></td></tr>
-<!-- <tr><td><dfn>ariaErrorMessageElement</dfn></td><td><pref>aria-errormessage</pref></td></tr> -->
+<tr><td><dfn>ariaErrorMessageElement</dfn></td><td><pref>aria-errormessage</pref></td></tr>
 <tr><td><dfn>ariaExpanded</dfn></td><td><sref>aria-expanded</sref></td></tr>
-<!-- <tr><td><dfn>ariaFlowToElements</dfn></td><td><pref>aria-flowto</pref></td></tr> -->
+<tr><td><dfn>ariaFlowToElements</dfn></td><td><pref>aria-flowto</pref></td></tr>
 <tr><td><dfn>ariaHasPopup</dfn></td><td><pref>aria-haspopup</pref></td></tr>
 <tr><td><dfn>ariaHidden</dfn></td><td><sref>aria-hidden</sref></td></tr>
 <tr><td><dfn>ariaInvalid</dfn></td><td><sref>aria-invalid</sref></td></tr>
 <tr><td><dfn>ariaKeyShortcuts</dfn></td><td><pref>aria-keyshortcuts</pref></td></tr>
 <tr><td><dfn>ariaLabel</dfn></td><td><pref>aria-label</pref></td></tr>
-<!-- <tr><td><dfn>ariaLabelledByElements</dfn></td><td><pref>aria-labelledby</pref></td></tr> -->
+<tr><td><dfn>ariaLabelledByElements</dfn></td><td><pref>aria-labelledby</pref></td></tr>
 <tr><td><dfn>ariaLevel</dfn></td><td><pref>aria-level</pref></td></tr>
 <tr><td><dfn>ariaLive</dfn></td><td><pref>aria-live</pref></td></tr>
 <tr><td><dfn>ariaModal</dfn></td><td><pref>aria-modal</pref></td></tr>
 <tr><td><dfn>ariaMultiLine</dfn></td><td><pref>aria-multiline</pref></td></tr>
 <tr><td><dfn>ariaMultiSelectable</dfn></td><td><pref>aria-multiselectable</pref></td></tr>
 <tr><td><dfn>ariaOrientation</dfn></td><td><pref>aria-orientation</pref></td></tr>
-<!-- <tr><td><dfn>ariaOwnsElements</dfn></td><td><pref>aria-owns</pref></td></tr> -->
+<tr><td><dfn>ariaOwnsElements</dfn></td><td><pref>aria-owns</pref></td></tr>
 <tr><td><dfn>ariaPlaceholder</dfn></td><td><pref>aria-placeholder</pref></td></tr>
 <tr><td><dfn>ariaPosInSet</dfn></td><td><pref>aria-posinset</pref></td></tr>
 <tr><td><dfn>ariaPressed</dfn></td><td><sref>aria-pressed</sref></td></tr>