base::Value cleanup: add simple Clang tool for structured cleanups

tools/clang/value_cleanup/tests/list-append-string-original.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/values.h"

[dcheng, 2016/06/02 08:04:49]

I didn't feel like duping the base::Value API here. Let me know if you feel
strongly about it.

[danakj, 2016/06/02 18:33:02]

I am unaware of reasons why this could be bad. *thinks*

I guess changes in base now have to change clang tools? Not really, they aren't
built by the waterfall. And I suspect this tool will not need to compile for too
long?

The amount of duping here would be fairly limited, but meh?

[dcheng, 2016/06/02 19:51:33]

Yeah I just don't want some weird instance where thing being matched in the test
doesn't actually match what Chromium is doing. Though I guess that's already
possible (since the test environment doesn't define OS_FOO, etc.)

This seems way easier though.

+
+void F() {
+  base::ListValue list;
+  list.Append(new base::StringValue("abc"));
+}