Codegen support for the argument definition test.

tests/language/argument_definition2_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.
+
+test1(bool passed, [a = 42]) {
+  if (passed) {
+    Expect.equals(54, a);
+    Expect.isTrue(?a);
+  } else {
+    Expect.equals(42, a);
+    Expect.isFalse(?a);
+  }
+  Expect.isTrue(?passed);
+}
+
+test2() {
+  var closure = (passed, [a = 42]) {
+    if (passed) {
+      Expect.equals(54, a);
+      Expect.isTrue(?a);
+    } else {
+      Expect.equals(42, a);
+      Expect.isFalse(?a);
+    }
+    Expect.isTrue(?passed);
+  };
+  closure(true, 54);
+  closure(false);
+}
+
+class A {
+  test3(bool passed, [a = 42]) {
+    if (passed) {
+      Expect.equals(54, a);
+      Expect.isTrue(?a);
+    } else {
+      Expect.equals(42, a);
+      Expect.isFalse(?a);
+    }
+    Expect.isTrue(?passed);
+  }
+}
+
+int inscrutable(int x) => x == 0 ? 0 : x | inscrutable(x & (x - 1));
+
+main() {
+  test1(true, 54);
+  test1(false);
+  test2();
+  new A().test3(true, 54);
+  new A().test3(false);
+
+  var things = [test1, test2, new A().test3];
+
+  var closure = things[inscrutable(0)];
+  closure(true, 54);
+  closure(false);
+
+  closure = things[inscrutable(1)];
+  closure();
+
+  closure = things[inscrutable(2)];
+  closure(true, 54);
+  closure(false);
+}