Allow menu-trigger to take a menu interface.

This should enable menus to be more easily extended for custom menu implementations.

src/lib/menu/menu-directive.ts

@@ -16,6 +16,7 @@ import {MenuPositionX, MenuPositionY} from './menu-positions';
 import {MdMenuInvalidPositionX, MdMenuInvalidPositionY} from './menu-errors';
 import {MdMenuItem} from './menu-item';
 import {UP_ARROW, DOWN_ARROW, TAB} from '../core';
+import {MdMenuInterface} from './menu-interface';
 
 @Component({
   moduleId: module.id,
@@ -26,7 +27,7 @@ import {UP_ARROW, DOWN_ARROW, TAB} from '../core';
   encapsulation: ViewEncapsulation.None,
   exportAs: 'mdMenu'
 })
-export class MdMenu {
+export class MdMenu implements MdMenuInterface {
   private _focusedItemIndex: number = 0;
 
   // config object to be passed into the menu's ngClass
@@ -58,7 +59,7 @@ export class MdMenu {
     }, {});
   }
 
-  @Output() close = new EventEmitter;
+  @Output() close = new EventEmitter<void>();
 
   /**
    * Focus the first item in the menu. This method is used by the menu trigger

src/lib/menu/menu-interface.ts

@@ -0,0 +1,10 @@
+import {EventEmitter, TemplateRef} from '@angular/core';
+import {MenuPositionX, MenuPositionY} from './menu-positions';
+
+export interface MdMenuInterface {
+  positionX: MenuPositionX;
+  positionY: MenuPositionY;
+  templateRef: TemplateRef<any>;
+  close: EventEmitter<void>;
+  _focusFirstItem: () => void;
+}

src/lib/menu/menu-trigger.ts

@@ -10,7 +10,7 @@ import {
     OnDestroy,
     Renderer
 } from '@angular/core';
-import {MdMenu} from './menu-directive';
+import {MdMenuInterface} from './menu-interface';
 import {MdMenuMissingError} from './menu-errors';
 import {
     ENTER,
@@ -47,7 +47,7 @@ export class MdMenuTrigger implements AfterViewInit, OnDestroy {
   // the first item of the list when the menu is opened via the keyboard
   private _openedFromKeyboard: boolean = false;
 
-  @Input('md-menu-trigger-for') menu: MdMenu;
+  @Input('md-menu-trigger-for') menu: MdMenuInterface;
   @Output() onMenuOpen = new EventEmitter();
   @Output() onMenuClose = new EventEmitter();
 
@@ -148,7 +148,7 @@ export class MdMenuTrigger implements AfterViewInit, OnDestroy {
    *  md-menu-trigger-for.  If not, an exception is thrown.
    */
   private _checkMenu() {
-    if (!this.menu || !(this.menu instanceof MdMenu)) {
+    if (!this.menu) {
       throw new MdMenuMissingError();
     }
   }

src/lib/menu/menu.ts

@@ -7,6 +7,8 @@ import {MdMenuTrigger} from './menu-trigger';
 export {MdMenu} from './menu-directive';
 export {MdMenuItem} from './menu-item';
 export {MdMenuTrigger} from './menu-trigger';
+export {MdMenuInterface} from './menu-interface';
+export {MenuPositionX, MenuPositionY} from './menu-positions';
 
 
 @NgModule({