fix(menu): closed nested menu chain when tabbing away (#7750)

Currently when tabbing inside a sub-menu, only the sub-menu is closed which restores focus to its parent. This is wrong, because it ends up sending the user back in the tab order. These changes close the whole chain of nested menus instead. For referece: https://www.w3.org/TR/wai-aria-practices-1.1/#menu

src/lib/menu/menu-directive.ts

@@ -196,8 +196,8 @@ export class MatMenu implements OnInit, AfterContentInit, MatMenuPanel, OnDestro
   set classList(classes: string) { this.panelClass = classes; }
 
   /** Event emitted when the menu is closed. */
-  @Output() readonly closed: EventEmitter<void | 'click' | 'keydown'> =
-      new EventEmitter<void | 'click' | 'keydown'>();
+  @Output() readonly closed: EventEmitter<void | 'click' | 'keydown' | 'tab'> =
+      new EventEmitter<void | 'click' | 'keydown' | 'tab'>();
 
   /**
    * Event emitted when the menu is closed.
@@ -217,7 +217,7 @@ export class MatMenu implements OnInit, AfterContentInit, MatMenuPanel, OnDestro
 
   ngAfterContentInit() {
     this._keyManager = new FocusKeyManager<MatMenuItem>(this.items).withWrap().withTypeAhead();
-    this._tabSubscription = this._keyManager.tabOut.subscribe(() => this.close.emit('keydown'));
+    this._tabSubscription = this._keyManager.tabOut.subscribe(() => this.close.emit('tab'));
   }
 
   ngOnDestroy() {

src/lib/menu/menu-panel.ts

@@ -21,7 +21,7 @@ export interface MatMenuPanel {
   yPosition: MenuPositionY;
   overlapTrigger: boolean;
   templateRef: TemplateRef<any>;
-  close: EventEmitter<void | 'click' | 'keydown'>;
+  close: EventEmitter<void | 'click' | 'keydown' | 'tab'>;
   parentMenu?: MatMenuPanel | undefined;
   direction?: Direction;
   focusFirstItem: (origin?: FocusOrigin) => void;

src/lib/menu/menu-trigger.ts

@@ -155,7 +155,7 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
       this._destroyMenu();
 
       // If a click closed the menu, we should close the entire chain of nested menus.
-      if (reason === 'click' && this._parentMenu) {
+      if ((reason === 'click' || reason === 'tab') && this._parentMenu) {
         this._parentMenu.closed.emit(reason);
       }
     });

src/lib/menu/menu.spec.ts

@@ -15,7 +15,7 @@ import {
 } from '@angular/core';
 import {Direction, Directionality} from '@angular/cdk/bidi';
 import {OverlayContainer, Overlay} from '@angular/cdk/overlay';
-import {ESCAPE, LEFT_ARROW, RIGHT_ARROW} from '@angular/cdk/keycodes';
+import {ESCAPE, LEFT_ARROW, RIGHT_ARROW, TAB} from '@angular/cdk/keycodes';
 import {
   MAT_MENU_DEFAULT_OPTIONS,
   MatMenu,
@@ -1168,6 +1168,28 @@ describe('MatMenu', () => {
       expect(overlay.querySelectorAll('.mat-menu-panel').length).toBe(0, 'Expected no open menus');
     }));
 
+    it('should close all of the menus when the user tabs away', fakeAsync(() => {
+      compileTestComponent();
+      instance.rootTriggerEl.nativeElement.click();
+      fixture.detectChanges();
+
+      instance.levelOneTrigger.openMenu();
+      fixture.detectChanges();
+
+      instance.levelTwoTrigger.openMenu();
+      fixture.detectChanges();
+
+      const menus = overlay.querySelectorAll('.mat-menu-panel');
+
+      expect(menus.length).toBe(3, 'Expected three open menus');
+
+      dispatchKeyboardEvent(menus[menus.length - 1], 'keydown', TAB);
+      fixture.detectChanges();
+      tick(500);
+
+      expect(overlay.querySelectorAll('.mat-menu-panel').length).toBe(0, 'Expected no open menus');
+    }));
+
     it('should set a class on the menu items that trigger a sub-menu', () => {
       compileTestComponent();
       instance.rootTrigger.openMenu();