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

tools/clang/value_cleanup/tests/list-value-append-expected.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"
+
+void F() {
+  base::ListValue list;
+  list.AppendBoolean(1 == 0);
+  list.AppendInteger(static_cast<unsigned char>(1.0));
+  list.AppendDouble(double{3});
+  list.AppendString("abc");
+}