[vm] Add test for certain cases of unreachable code

This is the follow-up for dart-lang/sdk@1d10e03.

Change-Id: Ifd35acb08904d34010ede0fe609076424d146374
Reviewed-on: https://dart-review.googlesource.com/c/81331
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Régis Crelier <regis@google.com>
Auto-Submit: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Régis Crelier <regis@google.com>

tests/language_2/vm/unreachable_code_test.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2018, 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.
+
+// Verifies that VM is able to handle certain cases of unreachable code.
+
+// VMOptions=--no_background_compilation --optimization_counter_threshold=10
+
+import "package:expect/expect.dart";
+
+class A {
+  dynamic next;
+}
+
+test1(A arg1, bool arg2, bool arg3) {
+  assert(arg1.next == (arg2 ?? arg3));
+}
+
+test2(A arg1, bool arg2, bool arg3) {
+  print(((throw 'Error') as dynamic).next == (arg2 ?? arg3));
+}
+
+void doTests() {
+  test1(new A(), null, null);
+  Expect.throws(() {
+    test2(new A(), null, null);
+  });
+}
+
+void main() {
+  for (int i = 0; i < 20; i++) {
+    doTests();
+  }
+}