Landing pull request 600. Remove jQuery.trim() to restore perf. Supplements #10773.

More Details:
 - https://github.com/jquery/jquery/pull/600
 - http://bugs.jquery.com/ticket/10773

src/attributes.js

@@ -355,21 +355,24 @@ jQuery.extend({
 		var propName, attrNames, name, l,
 			i = 0;
 
-		if ( value && typeof value === "string" && elem.nodeType === 1 ) {
-			attrNames = jQuery.trim( value ).toLowerCase().split( " " );
+		if ( value && elem.nodeType === 1 ) {
+			attrNames = value.toLowerCase().split( rspace );
 			l = attrNames.length;
 
 			for ( ; i < l; i++ ) {
 				name = attrNames[ i ];
-				propName = jQuery.propFix[ name ] || name;
 
-				// See #9699 for explanation of this approach (setting first, then removal)
-				jQuery.attr( elem, name, "" );
-				elem.removeAttribute( getSetAttribute ? name : propName );
+				if ( name ) {
+					propName = jQuery.propFix[ name ] || name;
 
-				// Set corresponding property to false for boolean attributes
-				if ( rboolean.test( name ) && propName in elem ) {
-					elem[ propName ] = false;
+					// See #9699 for explanation of this approach (setting first, then removal)
+					jQuery.attr( elem, name, "" );
+					elem.removeAttribute( getSetAttribute ? name : propName );
+
+					// Set corresponding property to false for boolean attributes
+					if ( rboolean.test( name ) && propName in elem ) {
+						elem[ propName ] = false;
+					}
 				}
 			}
 		}

test/unit/attributes.js

@@ -481,20 +481,7 @@ test("removeAttr(String)", function() {
 	}
 });
 
-test("removeAttr, #", function() {
-
-	var div = jQuery("<div />");
-
-	ok( div.removeAttr( "" ), "empty string" );
-	ok( div.removeAttr(), "nothing" );
-	ok( div.removeAttr( false ), "false" );
-	ok( div.removeAttr( true ), "true" );
-	ok( div.removeAttr({ }), "object" );
-	ok( div.removeAttr( function(){} ), "function" );
-
-});
-
-test("removeAttr(Multi String)", function() {
+test("removeAttr(Multi String, variable space width)", function() {
 	expect(8);
 
 	var div = jQuery("<div id='a' alt='b' title='c' rel='d'></div>"),
@@ -509,7 +496,7 @@ test("removeAttr(Multi String)", function() {
 		equal( div.attr(key), val, "Attribute `" + key + "` exists, and has a value of `" + val + "`" );
 	});
 
-	div.removeAttr( "id alt title rel " );
+	div.removeAttr( "id   alt title  rel  " );
 
 	jQuery.each( tests, function( key, val ) {
 		equal( div.attr(key), undefined, "Attribute `" + key + "` was removed" );