Added polyfill method to es6-promise. (#9627)

es6-promise/es6-promise-commonjs-tests.ts

@@ -1,6 +1,7 @@
 /// <reference path="es6-promise.d.ts" />
 
 import rsvp = require('es6-promise');
+rsvp.polyfill(); // Test for polyfill method existence
 var Promise = rsvp.Promise;
 
 var promiseString: Promise<string>,

es6-promise/es6-promise.d.ts

@@ -79,6 +79,7 @@ declare module 'es6-promise' {
 	var foo: typeof Promise; // Temp variable to reference Promise in local context
 	namespace rsvp {
 		export var Promise: typeof foo;
+		export function polyfill(): void;
 	}
 	export = rsvp;
 }