Implement proper scoping for "this" in arrow functions

test/mjsunit/harmony/arrow-functions-scoping.js

+// Copyright 2015 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.
+
+// Flags: --harmony-arrow-functions
+
+// The following are tests from:
+// http://wiki.ecmascript.org/doku.php?id=harmony:arrow_function_syntax
+var obj = {
+  method: function () {
+    return () => this;
+  }
+};
+assertSame(obj, obj.method()());
+
+var fake = { steal: obj.method() };
+assertSame(obj, fake.steal());
+
+var real = { borrow: obj.method };
+assertSame(real, real.borrow()());
+
+// Same, but using eval() for the arrow function.
+obj = {
+  method: function () {
+    return eval("() => this");
+  }
+};
+assertSame(obj, obj.method()());