menu: trigger ExpressionChangedAfterItHasBeenCheckedError aria-expanded: null in OnPush component

#### What is the expected behavior?
Error should not occur

#### What is the current behavior?
Repeatedly and quickly clicking on menu trigger button causes error

#### What are the steps to reproduce?
[StackBlitz](https://stackblitz.com/edit/angular-stgyux)
Click on menuTrigger repeatedly -> error shows in console

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Angular 7.1.0
Angular Material 7.1.0
Chrome Browser

#### Is there anything else we should know?
ChangeDetection: OnPush

ERROR
Error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'aria-expanded: true'. Current value: 'aria-expanded: null'.

Start with the linked StackBlitz reproduction using Angular and Angular Material 7.1.0, then repeatedly click the menu trigger in an OnPush component while watching the console. Trace the menu trigger's aria-expanded changes and determine why the checked value changes to null; done means the reproduction no longer reports ExpressionChangedAfterItHasBeenCheckedError.

Written by the indexing model from the issue text.