Use Scope::function_kind_ to distinguish arrow function scopes

test/mjsunit/es6/regress/regress-4466.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.
+
+"use strict";
+
+class Parent {
+  parentMethod(x, y) {
+    assertEquals(42, x);
+    assertEquals('hello world', y);
+  }
+}
+
+class Child extends Parent {
+  method(x) {
+    let outer = (y) => {

[Dan Ehrenberg, 2015/10/07 00:25:41]

You might want to reference y here, as the original bug report noted that not
referencing it suppresses the issue (by making it so that the scope is removed
earlier?). Did you test this against HEAD to ensure that it fails?

[adamk, 2015/10/07 00:34:31]

Yes, this test fails without this patch. The usages in the inner arrow function
are sufficient to force the outer scopes to be reified.

+      let inner = () => {
+        super.parentMethod(x, y);
+      };
+      inner();
+    };
+    outer('hello world');
+  }
+}
+
+new Child().method(42);