Deferred: Backwards-compatible standards interoperability

Fixes gh-1722
Closes gh-1996

(cherry picked from commit 555a50d340)

build/tasks/promises-aplus-tests.js

@@ -0,0 +1,20 @@
+module.exports = function( grunt ) {
+
+	"use strict";
+
+	var spawn = require( "child_process" ).spawn;
+
+	grunt.registerTask( "promises-aplus-tests", function() {
+		var done = this.async();
+		spawn(
+			"node",
+			[
+				"./node_modules/.bin/promises-aplus-tests",
+				"test/promises-aplus-adapter.js"
+			],
+			{ stdio: "inherit" }
+		).on( "close", function( code ) {
+			done( code === 0 );
+		});
+	});
+};