Remove default value for aria-expanded from combobox role (#943)

* Remove default value for aria-expanded from combobox role
* Update combobox role prose to better reflect removal of default aria-expanded value

index.html

@@ -1799,7 +1799,7 @@ <h2>Definition of Roles</h2>
 			<div class="role-description">
 				<p>A composite <rref>widget</rref> containing a single-line <rref>textbox</rref> and another element, such as a <rref>listbox</rref> or <rref>grid</rref>, that can dynamically pop up to help the user set the value of the <rref>textbox</rref>.</p>
 				<p>Authors MUST ensure an element with role <code>combobox</code> contains or owns a text input element with role <rref>textbox</rref> or <rref>searchbox</rref> and that the text input has <pref>aria-multiline</pref> set to <code>false</code>. If the <code>combobox</code> provides autocompletion behavior for the text input as described in <pref>aria-autocomplete</pref>, authors MUST set <pref>aria-autocomplete</pref> on the <rref>textbox</rref> element to the value that corresponds to the provided behavior.</p>
-				<p>Typically, the default state of a <code>combobox</code> is collapsed. In the collapsed state, only the <rref>textbox</rref> element of a <code>combobox</code> is visible. A <code>combobox</code> is said to be expanded when both the <rref>textbox</rref> and a secondary element that serves as its popup are visible. Authors MUST set <sref>aria-expanded</sref> to <code>true</code> on an element with role <code>combobox</code> when it is expanded and <code>false</code> when it is collapsed. Elements with the role <code>combobox</code> have an implicit <sref>aria-expanded</sref> value of <code>false</code>.</p>
+				<p>Typically, the initial state of a <code>combobox</code> is collapsed. In the collapsed state, only the <rref>textbox</rref> element of a <code>combobox</code> is visible. A <code>combobox</code> is said to be expanded when both the <rref>textbox</rref> and a secondary element that serves as its popup are visible. Authors MUST set <sref>aria-expanded</sref> to <code>true</code> on an element with role <code>combobox</code> when it is expanded and <code>false</code> when it is collapsed.</p>
 				<p>When a <code>combobox</code> is expanded, authors MUST ensure it contains or owns an element that has a role of <rref>listbox</rref>, <rref>tree</rref>, <rref>grid</rref>, or <rref>dialog</rref>. This element is the <code>combobox</code> popup. When the <code>combobox</code> is expanded, authors MUST set <pref>aria-controls</pref> on the <rref>textbox</rref> element to a value that refers to the <code>combobox</code> popup element.</p>
 				<p>Elements with the role <code>combobox</code> have an implicit <pref>aria-haspopup</pref> value of <code>listbox</code>. If the <code>combobox</code> popup element has a role other than <rref>listbox</rref>, authors MUST specify a value for <pref>aria-haspopup</pref> that corresponds to the type of its popup.</p>
 				<p>To be <a>keyboard accessible</a>, authors SHOULD manage focus of descendants for all instances of this <a>role</a>, as described in <a href="#managingfocus">Managing Focus</a>. When a <code>combobox</code> receives focus, authors SHOULD ensure focus is placed on the <rref>textbox</rref> element.</p>
@@ -1912,7 +1912,6 @@ <h2>Definition of Roles</h2>
 					<tr>
 						<th class="implicit-values-head" scope="row">Implicit Value for Role:</th>
 						<td class="implicit-values">
-							Default for <sref>aria-expanded</sref> is <code class="default">false</code>.<br/>
 							Default for <pref>aria-haspopup</pref> is <code class="default">listbox</code>.<br/>
 						</td>
 					</tr>