WIP [esnext] implement async iteration proposal

test/test262/local-tests/test/language/expressions/async-generators/early-errors-expression-NSPL-with-USD.js

Index: test/test262/local-tests/test/language/expressions/async-generators/early-errors-expression-NSPL-with-USD.js
diff --git a/test/test262/local-tests/test/language/expressions/async-generators/early-errors-expression-NSPL-with-USD.js b/test/test262/local-tests/test/language/expressions/async-generators/early-errors-expression-NSPL-with-USD.js
new file mode 100644
index 0000000000000000000000000000000000000000..b887c2ce2709218fff2ee664186542a17e35a7a6
--- /dev/null
+++ b/test/test262/local-tests/test/language/expressions/async-generators/early-errors-expression-NSPL-with-USD.js
@@ -0,0 +1,15 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Caitlin Potter <caitp@igalia.com>
+esid: pending
+description: >
+  It is a Syntax Error if ContainsUseStrict of AsyncGeneratorBody is true and
+  IsSimpleParameterList of UniqueFormalParameters is false.
+negative:
+  phase: early
+  type: SyntaxError
+---*/
+
+(async function*(x = 1) {"use strict"});