Selectmenu: Heed dividerTheme if there are optgroup children

Fixes gh-7080
Closes gh-7945

js/widgets/forms/select.custom.js

@@ -196,7 +196,8 @@ $.widget( "mobile.selectmenu", $.mobile.selectmenu, {
 		overlayTheme = o.overlayTheme || o.theme || null;
 		overlayThemeAttr = overlayTheme ? ( " data-" + $.mobile.ns +
 			"overlay-theme='" + overlayTheme + "'" ) : "";
-		dividerThemeAttr = ( o.dividerTheme && isMultiple ) ? ( " data-" + $.mobile.ns + "divider-theme='" + o.dividerTheme + "'" ) : "";
+		dividerThemeAttr = ( o.dividerTheme && this.element.children( "optgroup" ).length > 0 ) ?
+			( " data-" + $.mobile.ns + "divider-theme='" + o.dividerTheme + "'" ) : "";
 		menuPage = $( "<div data-" + $.mobile.ns + "role='dialog' class='ui-selectmenu'" +
 			themeAttr + overlayThemeAttr + ">" +
 			"<div data-" + $.mobile.ns + "role='header'>" +

tests/integration/select/index.html

@@ -533,7 +533,7 @@
 		</select>
 
 		<div data-nstest-role="fieldcontain" id="optgroup-and-placeholder-container">
-			<select name="optgroup-and-placeholder" id="optgroup-and-placeholder" data-nstest-native-menu="false">
+			<select name="optgroup-and-placeholder" data-nstest-divider-theme="b" id="optgroup-and-placeholder" data-nstest-native-menu="false">
 				<option>Choose shipping method</option>
 				<optgroup label="USPS">
 					<option value="standard" selected>Standard: 7 day</option>

tests/integration/select/select_core.js

@@ -41,10 +41,14 @@
 	});
 
 	asyncTest( "placeholder correctly gets ui-screen-hidden class after rebuilding", function() {
+		expect( 3 );
+
 		$.testHelper.sequence( [
 			function() {
 				// bring up the optgroup menu
 				ok( $( "#optgroup-and-placeholder-container a" ).length > 0, "there is in fact a button in the page" );
+				deepEqual( $( "#optgroup-and-placeholder-menu li.ui-li-divider" )
+					.first().hasClass( "ui-bar-b" ), true, "Optgroup header has swatch b" );
 				$( "#optgroup-and-placeholder-container a" ).trigger( "click" );
 			},