Bug, feature request, or proposal:

Feature request

Background

We couldn't use mat-menu directly because it didn't support our use cases. As a result, the code base I am working on has following components:

• own menu item component that wraps mat-menu-item.
• our own menu component that extends mat-menu.
• our own trigger directive that forks of matMenuTriggerFor

This worked for us, but we needed to set private _triggersSubMenu property here: https://github.com/angular/material2/blob/be84566caa61e4d59a93be1a84dbe7cfe090c8c1/src/lib/menu/menu-item.ts#L68

Should mat-menu-item take this as an @input() to make this component more extensible?