Revert "Reland "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);
-    }
-  }
-}