Core: Only use mousedown to prevent text selection in browsers that d…

…on't support selectstart. Fixes #6080 - Core: disableSelection() disables select elements in Chrome.

ui/jquery.ui.core.js

@@ -118,9 +118,8 @@ $.fn.extend({
 	},
 
 	disableSelection: function() {
-		return this.bind(
-			"mousedown.ui-disableSelection selectstart.ui-disableSelection",
-			function( event ) {
+		return this.bind( $.support.selectstart ? "selectstart" : "mousedown" +
+			".ui-disableSelection", function( event ) {
 				event.preventDefault();
 			});
 	},
@@ -217,8 +216,8 @@ $.extend( $.expr[ ":" ], {
 
 // support
 $(function() {
-	var div = document.createElement( "div" ),
-		body = document.body;
+	var body = document.body,
+		div = body.appendChild( div = document.createElement( "div" ) );
 
 	$.extend( div.style, {
 		minHeight: "100px",
@@ -227,7 +226,9 @@ $(function() {
 		borderWidth: 0
 	});
 
-	$.support.minHeight = body.appendChild( div ).offsetHeight === 100;
+	$.support.minHeight = div.offsetHeight === 100;
+	$.support.selectstart = "onselectstart" in div;
+
 	// set display to none to avoid a layout bug in IE
 	// http://dev.jquery.com/ticket/4014
 	body.removeChild( div ).style.display = "none";