Add assert-in-initializer-list to formal specification.

tests/language/assertion_initializer_const_function_test.dart

+// Copyright (c) 201, 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.
+// VMOptions=--assert_initializer
+//
+// Dart test program testing assert statements.
+
+import "package:expect/expect.dart";
+
+class C {
+  static bool staticTrue() => true;
+  final int x;
+  const C(this.x);
+  // The expression *is* compile-time constant, but not a bool value.
+  // Static warning, runtime always fails assertion.
+  const C.bc01(this.x, y)
+      : assert(staticTrue)  //# 01: static type warning
+      ;
+}
+
+main() {
+  bool checkedMode = false;
+  assert(checkedMode = true);
+  if (checkedMode) {
+    Expect.throws(() => new C.bc01(1, 2), (e) => e is AssertionError);
+  } else {
+    Expect.equals(1, new C.bc01(1, 2).x);
+  }
+}