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

tests/language/logical_expression4_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";
-
-int globalCounter = 0;
-
-bool nonInlinedNumTypeCheck(Object object) {
-  if (new DateTime.now().millisecondsSinceEpoch == 42) {
-    return nonInlinedNumTypeCheck(object);
-  }
-  return object is num;
-}
-
-int confuse(x) {
-  if (new DateTime.now().millisecondsSinceEpoch == 42) return confuse(x - 1);
-  return x;
-}
-
-main() {
-  var o = [ "foo", 499 ][confuse(0)];
-
-  // The is-checks in the '!' must not be propagated to the if-body.
-  // This was a bug in dart2js.
-  if (!(o is num && o is num)) {
-    Expect.isFalse((nonInlinedNumTypeCheck(o)));
-  }
-}