Added support for ES2017 async functions

spec/helpers/asyncAwait.js

@@ -0,0 +1,27 @@
+(function(env) {
+  function getAsyncCtor() {
+    try {
+      eval("var func = async function(){};");
+    } catch (e) {
+      return null;
+    }
+
+    return Object.getPrototypeOf(func).constructor;
+  }
+
+  function hasAsyncAwaitSupport() {
+    return getAsyncCtor() !== null;
+  }
+
+  env.makeAsyncAwaitFunction = function() {
+    var AsyncFunction = getAsyncCtor();
+    return new AsyncFunction("");
+  };
+
+  env.requireAsyncAwait = function() {
+    if (!hasAsyncAwaitSupport()) {
+      env.pending("Environment does not support async/await functions");
+    }
+  };
+})(jasmine.getEnv());
+