Add more tested features to closure_test

tests/compiler/dart2js/closure/data/captured_variable.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*readParameterInClosure:*/
+readParameterInClosure(/**/ parameter) {
+  /*captured=[parameter],free=[parameter]*/ func() => parameter;
+  return func;
+}
+
+/*writeParameterInClosure:boxed=[parameter],captured=[parameter],requiresBox*/
+writeParameterInClosure(/*boxed*/ parameter) {
+  /*boxed=[parameter],captured=[parameter],free=[box,parameter]*/ func() {
+    parameter = 42;
+  }
+
+  return func;
+}
+
+/*readLocalInClosure:*/
+readLocalInClosure(/**/ parameter) {
+  var /**/ local = parameter;
+  /*captured=[local],free=[local]*/ func() => local;
+  return func;
+}
+
+/*writeLocalInClosure:boxed=[local],captured=[local],requiresBox*/
+writeLocalInClosure(/**/ parameter) {
+  // ignore: UNUSED_LOCAL_VARIABLE
+  var /*boxed*/ local = parameter;
+  /*boxed=[local],captured=[local],free=[box,local]*/ func() {
+    local = 42;
+  }
+
+  return func;
+}
+
+main() {
+  readParameterInClosure(null);
+  writeParameterInClosure(null);
+  readLocalInClosure(null);
+  writeLocalInClosure(null);
+}