Fix function name inference corruption for async functions

test/mjsunit/regress/regress-cr-658267.js

Index: test/mjsunit/regress/regress-cr-658267.js
diff --git a/test/mjsunit/regress/regress-cr-658267.js b/test/mjsunit/regress/regress-cr-658267.js
new file mode 100644
index 0000000000000000000000000000000000000000..9caada7954f05c19daebb67fc65e162348055909
--- /dev/null
+++ b/test/mjsunit/regress/regress-cr-658267.js
@@ -0,0 +1,5 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+assertThrows("class D extends async() =>", SyntaxError);