Revert "Fix bad type-inferrence for logical expressions."

tests/language/logical_expression2_test.dart

-// Copyright (c) 2014, 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 "package:expect/expect.dart";
-
-// Regression test for issue 17149.
-
-int globalCounter = 0;
-
-void nonInlinedUse(Object object) {
-  if (new DateTime.now().millisecondsSinceEpoch == 42) nonInlinedUse(object);
-  if (object is! String) globalCounter++;
-}
-
-int confuse(x) {
-  if (new DateTime.now().millisecondsSinceEpoch == 42) return confuse(x - 1);
-  return x;
-}
-
-main() {
-  var o = [ "foo", 499 ][confuse(1)];
-
-  // The `o is String` check in the rhs of the logical or must not be
-  // propagated to the `if` body.
-  if ((o is num) ||
-      (o is String && true)) {
-    nonInlinedUse(o);
-  }
-  Expect.equals(1, globalCounter);
-}