Remove unnecessary contexts in closure conversion

pkg/kernel/testcases/closures/contexts_in_field_initializers.dart

Index: pkg/kernel/testcases/closures/contexts_in_field_initializers.dart
diff --git a/pkg/kernel/testcases/closures/contexts_in_field_initializers.dart b/pkg/kernel/testcases/closures/contexts_in_field_initializers.dart
new file mode 100644
index 0000000000000000000000000000000000000000..0be4a67f58fb604f86c809f5a92da9a2302a5398
--- /dev/null
+++ b/pkg/kernel/testcases/closures/contexts_in_field_initializers.dart
@@ -0,0 +1,19 @@
+// 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.
+
+// The purpose of this test is to detect that no unnecessary contexts are
+// created when a constructor parameter is used in its field initializers.  No
+// contexts should be created either in the initializer or in the constructor
+// body.
+
+class X {}
+
+class A {
+  X x;
+  A(this.x) {}
+}
+
+main() {
+  A a = new A(new X());
+}