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

src/material-experimental/mdc-menu/menu.spec.ts

@@ -1260,6 +1260,9 @@ describe('MDC-based 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', () => {

src/material/menu/menu-trigger.ts

@@ -291,6 +291,13 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
     }
   }
 
+  /**
+   * Updates the position of the menu to ensure that it fits all options within the viewport.
+   */
+  updatePosition(): void {
+    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 +1280,9 @@ 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', () => {

tools/public_api_guard/material/menu.d.ts

@@ -173,6 +173,7 @@ export declare class MatMenuTrigger implements AfterContentInit, OnDestroy {
     openMenu(): void;
     toggleMenu(): void;
     triggersSubmenu(): boolean;
+    updatePosition(): void;
     static ɵdir: i0.ɵɵDirectiveDefWithMeta<MatMenuTrigger, "[mat-menu-trigger-for], [matMenuTriggerFor]", ["matMenuTrigger"], { "_deprecatedMatMenuTriggerFor": "mat-menu-trigger-for"; "menu": "matMenuTriggerFor"; "menuData": "matMenuTriggerData"; "restoreFocus": "matMenuTriggerRestoreFocus"; }, { "menuOpened": "menuOpened"; "onMenuOpen": "onMenuOpen"; "menuClosed": "menuClosed"; "onMenuClose": "onMenuClose"; }, never>;
     static ɵfac: i0.ɵɵFactoryDef<MatMenuTrigger, [null, null, null, null, { optional: true; }, { optional: true; self: true; }, { optional: true; }, null]>;
 }