Support closures inside initializers.

tests/language/closure_in_initializer_test.dart

+// Copyright (c) 2012, 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.
+
+class A {
+  var f;
+  var g;
+  A(a) : f = (() => 42 + a), g = (() => ++a) {
+    a = 4;
+  }
+}
+
+class B extends A {
+  B() : super(42);
+}
+
+class C extends A {
+  var h;
+  C(a) : super(42), h = (() => ++a);
+}
+
+main() {
+  var a = new A(1);
+  Expect.equals(46, a.f());
+  Expect.equals(5, a.g());
+  Expect.equals(47, a.f());
+
+  a = new B();
+  Expect.equals(46, a.f());
+  Expect.equals(5, a.g());
+  Expect.equals(47, a.f());
+
+  a = new C(0);
+  Expect.equals(46, a.f());
+  Expect.equals(5, a.g());
+  Expect.equals(47, a.f());
+  Expect.equals(1, a.h());
+  Expect.equals(2, a.h());
+  Expect.equals(47, a.f());
+  Expect.equals(6, a.g());
+  Expect.equals(48, a.f());
+}