New tests for initializing formal access.

tests/language/initializing_formal_promotion_test.dart

 // Copyright (c) 2016, 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.
 //
 // DartOptions=--initializing-formal-access
 
 import "package:expect/expect.dart";
 
-class C {
-  final int x;
-  final int y;
+class B {}
 
-  const C.constant(this.x) : y = x + 1;
-
-  C(this.x) : y = x + 1 {
-    int z = x + 2;
-    assert(z == y + 1);
+class A {
+  B x, y;
+  A(this.x) {
+    // Promote to subtype.
+    if (x is C) y = x.x;
+    // Promotion fails, not a subtype.
+    if (x is A) y = x;
   }
 }
 
+class C extends A implements B {
+  C(B x) : super(x);
+}
+
 main() {
-  C c = new C(2);
-  Expect.equals(c.x, 2);
-  Expect.equals(c.y, 3);
-  const C cc = const C.constant(4);
-  Expect.equals(cc.x, 4);
-  Expect.equals(cc.y, 5);
+  C c2 = new C(null);
+  C cc = new C(c2);
+  Expect.equals(c2.y, null);
+  Expect.equals(cc.y, c2);
 }