Merge more Kernel infrastructure from kernel_sdk SDK fork.

tests/kernel/unsorted/expect.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.
+
+import 'dart:io' as io;
+
+// We use this class until we support more language features to use
+// `package:expect`.
+class Expect {
+  static void isTrue(bool condition) {
+    if (!condition) {
+      print("Expect.isTrue(cond) failed. io.exit(1)ing");
+      io.exit(1);
+    }
+  }
+}