Move some properties from "required" to "supported" on slider role (#946

)

Addresses #860
* Reword slider role prose to reflect that aria-valuemin, valuemax are now supported, not required
* Remove aria-valuenow repair techniques from inline in the slider role
* Make fallback table more robust for aria-valuenow on slider role
* Add pointer to the fallback table from slider role
* Remove supported but not required attrs on slider from the author error handling table

index.html

@@ -6509,16 +6509,14 @@ <h5>Presentational Roles Conflict Resolution</h5>
 		<div class="role" id="slider">
 			<rdef>slider</rdef>
 			<div class="role-description">
-				<p>A user input where the user selects a value from within a given range.</p>
+				<p>An input where the user selects a value from within a given range.</p>
 				<p>A slider represents the current value and range of possible values via the size of the slider and position of the thumb. It is typically possible to add or subtract to the value by using directional keys such as arrow keys.</p>
-				<p>Authors MUST set the <pref>aria-valuemin</pref>, <pref>aria-valuemax</pref>, and <pref>aria-valuenow</pref> attributes.	If missing, their implicit values follow the same rules as the <a href="https://www.w3.org/TR/html5/forms.html#range-state-%28type=range%29" title="Range state">HTML range input type</a>:</p>
+				<p>Authors MAY set the <pref>aria-valuemin</pref> and <pref>aria-valuemax</pref> attributes.	Otherwise, their implicit values follow the same rules as the <a href="https://www.w3.org/TR/html5/forms.html#range-state-%28type=range%29" title="Range state">HTML range input type</a>:</p>
 				<ul>
 				    <li>If <code>aria-valuemin</code> is missing or not a <a href="#valuetype_number">number</a>, it defaults to 0 (zero). </li>
 				    <li>If <code>aria-valuemax</code> is missing or not a <a href="#valuetype_number">number</a>, it defaults to 100. </li>
-				    <li>If <code>aria-valuenow</code> is missing or not a <a href="#valuetype_number">number</a>, it defaults to the value half way between <code>aria-valuemin</code> and <code>aria-valuemax</code>. </li>
-				    <li>If <code>aria-valuenow</code> is present but less than <code>aria-valuemin</code>, it defaults to the value of <code>aria-valuemin</code>. </li>
-				    <li>If <code>aria-valuenow</code> is present but greater than <code>aria-valuemax</code>, it defaults to the value of <code>aria-valuemax</code>. </li>
 				</ul>
+				<p>Authors MUST set the <pref>aria-valuenow</pref> attribute. If aria-valuenow is missing or has an unexpected value, browsers MAY implement the repair techniques specified in the <a href="authorErrorDefaultValuesTable" class="specref">section describing handling author errors in states and properties</a>, which are equivalent to the repair techniques for the <a href="https://www.w3.org/TR/html5/forms.html#range-state-%28type=range%29" title="Range state">HTML range input type</a>.</p>
 				<p>Elements with the role <code>slider</code> have an implicit <pref>aria-orientation</pref> value of <code>horizontal</code>.</p>
 			</div>
 			<table class="role-features">
@@ -6565,8 +6563,6 @@ <h5>Presentational Roles Conflict Resolution</h5>
 						<th class="role-required-properties-head">Required States and Properties:</th>
 						<td class="role-required-properties">
 							<ul>
-								<li><pref>aria-valuemax</pref></li>
-								<li><pref>aria-valuemin</pref></li>
 								<li><pref>aria-valuenow</pref></li>
 							</ul>
 						</td>
@@ -6577,6 +6573,8 @@ <h5>Presentational Roles Conflict Resolution</h5>
 							<ul>
 								<li><pref>aria-orientation</pref></li>
 								<li><pref>aria-readonly</pref></li>
+								<li><pref>aria-valuemax</pref></li>
+								<li><pref>aria-valuemin</pref></li>
 							</ul>
 						</td>
 					</tr>
@@ -6609,8 +6607,7 @@ <h5>Presentational Roles Conflict Resolution</h5>
 						<td class="implicit-values">
 							Default for <pref>aria-orientation</pref> is <code class="default">horizontal</code>. <br/>
 							Default for <pref>aria-valuemin</pref> is <code class="default">0</code>. <br/>
-							Default for <pref>aria-valuemax</pref> is <code class="default">100</code>. <br/>
-							Default for <pref>aria-valuenow</pref> is half way between <code class="default">aria-valuemax</code> and <code class="default">aria-valuemin</code>.
+							Default for <pref>aria-valuemax</pref> is <code class="default">100</code>.
 						</td>
 					</tr>
 				</tbody>
@@ -11423,20 +11420,10 @@ <h3>States and Properties</h3>
 					<td><pref>aria-valuenow</pref></td>
 					<td><code>(aria-valuemax - aria-valuemin) / 2</code></td>
 				</tr>
-				<tr>
-					<td><rref>slider</rref></td>
-					<td><pref>aria-valuemax</pref></td>
-					<td><code>100</code></td>
-				</tr>
-				<tr>
-					<td><rref>slider</rref></td>
-					<td><pref>aria-valuemin</pref></td>
-					<td><code>0</code></td>
-				</tr>
 				<tr>
 					<td><rref>slider</rref></td>
 					<td><pref>aria-valuenow</pref></td>
-					<td><code>(aria-valuemax - aria-valuemin) / 2</code></td>
+					<td>If missing or not a <a href="#valuetype_number">number</a>,<code>(aria-valuemax - aria-valuemin) / 2</code>. If present but less than <code>aria-valuemin</code>, the value of <code>aria-valuemin</code>. If present but greater than <code>aria-valuemax</code>, the value of <code>aria-valuemax</code>. </td>
 				</tr>
 				<tr>
 					<td><rref>spinbutton</rref></td>
@@ -11705,7 +11692,7 @@ <h2>Change Log</h2>
 		<h2>Substantive changes since the last public working draft</h2>
 		<ul>
 			<!-- EdNote: After each WD publish, move contents of this list into the next one below. -->
-			<li>04-June-2019: Make aria-valuemin and aria-valuemax supported, rather than required, properties of focusable separator</li>
+			<li>04-June-2019: Make aria-valuemin and aria-valuemax supported, rather than required, properties of focusable separator and slider</li>
 			<li>27-Mar-2019: Add Translatable States and Properties Section</li>
 			<li>31-Jan-2019: Change the superclass of range from widget to structure.</li>
 			<li>23-Jan-2019: Removed Default value of aria-checked from manuitemcheckbox and menuitemradio roles</li>