Menu: Ignore bubbled mouseenter events on parent items

Test uses QUnit 2.x API - inconsistent with the other tests, but also
a good reference.

Fixes #11641
Closes gh-1535

tests/unit/menu/menu_events.js

@@ -111,6 +111,48 @@ asyncTest( "handle focus of menu with active item", function() {
	});
});

test( "handle mouseenter on nested menu item", function( assert ) {
	assert.expect( 8 );
	$.ui.menu.prototype.delay = 1;
	var activeItem,
		done = assert.async(),
		element = $( "#menu2" ).menu();

	element
		.menu( "previous" )
		.menu( "expand" );

	function checkSubmenus() {
		equal( element.find( "ul[aria-expanded='true']" ).length, 2, "both submenus expanded" );
	}
	function menumouseenter1() {
		element.menu( "expand" );
		setTimeout( menumouseenter2, 25 );
	}
	function menumouseenter2() {
		checkSubmenus();
		activeItem = $( "#" + element.attr( "aria-activedescendant" ) );
		assert.hasClasses( activeItem, "ui-state-active" );
		activeItem.trigger( "mouseleave" );
		setTimeout( menumouseenter3, 25 );
	}
	function menumouseenter3() {
		checkSubmenus();
		assert.lacksClasses( activeItem, "ui-state-active" );
		activeItem.trigger( "mouseenter" );
		setTimeout( menumouseenter4, 25 );
	}
	function menumouseenter4() {
		checkSubmenus();
		activeItem.parents( ".ui-menu-item" ).each( function( index, item ) {
			assert.hasClasses( $( item ).children( ".ui-menu-item-wrapper" ), "ui-state-active" );
		} );
		$.ui.menu.prototype.delay = 300;
		done();
	}
	setTimeout( menumouseenter1, 25 );
} );

asyncTest( "handle submenu auto collapse: mouseleave, default markup", function() {
	expect( 4 );
	$.ui.menu.prototype.delay = 1;

ui/menu.js

@@ -108,13 +108,22 @@ return $.widget( "ui.menu", {
				}
			},
			"mouseenter .ui-menu-item": function( event ) {

				// Ignore mouse events while typeahead is active, see #10458.
				// Prevents focusing the wrong item when typeahead causes a scroll while the mouse
				// is over an item in the menu
				if ( this.previousFilter ) {
					return;
				}
				var target = $( event.currentTarget );

				var actualTarget = $( event.target ).closest( ".ui-menu-item" ),
					target = $( event.currentTarget );

				// Ignore bubbled events on parent items, see #11641
				if ( actualTarget[ 0 ] !== target[ 0 ] ) {
					return;
				}

				// Remove ui-state-active class from siblings of the newly focused menu item
				// to avoid a jump caused by adjacent elements both having a class with a border
				this._removeClass( target.siblings().children( ".ui-state-active" ),