feat(material/menu): allow focus origin to be optional input in focus method

src/material/menu/menu-item.ts

@@ -94,8 +94,8 @@ export class MatMenuItem extends _MatMenuItemMixinBase
   }
 
   /** Focuses the menu item. */
-  focus(origin: FocusOrigin = 'program', options?: FocusOptions): void {
-    if (this._focusMonitor) {
+  focus(origin?: FocusOrigin, options?: FocusOptions): void {
+    if (this._focusMonitor && origin) {
       this._focusMonitor.focusVia(this._getHostElement(), origin, options);
     } else {
       this._getHostElement().focus(options);

src/material/menu/menu-trigger.ts

@@ -275,8 +275,8 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
    * Focuses the menu trigger.
    * @param origin Source of the menu trigger's focus.
    */
-  focus(origin: FocusOrigin = 'program', options?: FocusOptions) {
-    if (this._focusMonitor) {
+  focus(origin?: FocusOrigin, options?: FocusOptions) {
+    if (this._focusMonitor && origin) {
       this._focusMonitor.focusVia(this._element, origin, options);
     } else {
       this._element.nativeElement.focus(options);

src/material/menu/menu.spec.ts

@@ -615,6 +615,25 @@ describe('MatMenu', () => {
     expect(items.every(item => item.getAttribute('role') === 'menuitemcheckbox')).toBe(true);
   });
 
+  it('should not change focus origin if origin not specified for menu items', () => {
+    const fixture = createComponent(MenuWithCheckboxItems);
+    fixture.detectChanges();
+    fixture.componentInstance.trigger.openMenu();
+    fixture.detectChanges();
+
+    let [firstMenuItemDebugEl, secondMenuItemDebugEl] =
+           fixture.debugElement.queryAll(By.css('.mat-menu-item'))!;
+
+    const firstMenuItemInstance = firstMenuItemDebugEl.componentInstance as MatMenuItem;
+    const secondMenuItemInstance = secondMenuItemDebugEl.componentInstance as MatMenuItem;
+
+    firstMenuItemInstance.focus('mouse');
+    secondMenuItemInstance.focus();
+
+    expect(secondMenuItemDebugEl.nativeElement.classList).toContain('cdk-focused');
+    expect(secondMenuItemDebugEl.nativeElement.classList).toContain('cdk-mouse-focused');
+  });
+
   it('should not throw an error on destroy', () => {
     const fixture = createComponent(SimpleMenu, [], [FakeIcon]);
     expect(fixture.destroy.bind(fixture)).not.toThrow();
@@ -2006,6 +2025,24 @@ describe('MatMenu', () => {
             .toContain('mat-elevation-z4', 'Expected menu to have the proper updated elevation.');
       }));
 
+        it('should not change focus origin if origin not specified for menu trigger',
+      fakeAsync(() => {
+        compileTestComponent();
+
+        instance.levelOneTrigger.openMenu();
+        instance.levelOneTrigger.focus('mouse');
+        fixture.detectChanges();
+
+        instance.levelTwoTrigger.focus();
+        fixture.detectChanges();
+        tick(500);
+
+        const levelTwoTrigger = overlay.querySelector('#level-two-trigger')! as HTMLElement;
+
+        expect(levelTwoTrigger.classList).toContain('cdk-focused');
+        expect(levelTwoTrigger.classList).toContain('cdk-mouse-focused');
+      }));
+
     it('should not increase the elevation if the user specified a custom one', () => {
       const elevationFixture = createComponent(NestedMenuCustomElevation);