feat(material/menu): allow updating menu position a la autocomplete

Author: terencehonles

src/material/menu/menu-trigger.ts

@@ -291,6 +291,15 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
     }
   }
 
+  /**
+   * Updates the position of the menu to ensure that it fits all options within the viewport.
+   */
+  updatePosition(): void {
+    if (this._overlayRef) {
+      this._overlayRef.updatePosition();
+    }
+  }
+
   /** Closes the menu and does the necessary cleanup. */
   private _destroyMenu(reason: MenuCloseReason) {
     if (!this._overlayRef || !this.menuOpen) {

src/material/menu/menu.spec.ts

@@ -1280,6 +1280,10 @@ describe('MatMenu', () => {
           .toBe(Math.floor(trigger.getBoundingClientRect().bottom), 'Expected menu to open below');
     });
 
+    it('should not throw if a menu reposition is requested while the menu is closed', () => {
+      expect(fixture.componentInstance.trigger.updatePosition()).not.toThrow();
+    });
+
   });
 
   describe('fallback positions', () => {