Implement inference tests for logical operators.

pkg/front_end/testcases/inference_new/infer_logical.dart

+// Copyright (c) 2017, 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.
+
+/*@testedFeatures=inference*/
+library test;
+
+T f<T>() => null;
+
+var /*@topType=bool*/ x = /*@typeArgs=bool*/ f() || /*@typeArgs=bool*/ f();
+var /*@topType=bool*/ y = /*@typeArgs=bool*/ f() && /*@typeArgs=bool*/ f();
+
+void test() {
+  var /*@type=bool*/ x = /*@typeArgs=bool*/ f() || /*@typeArgs=bool*/ f();
+  var /*@type=bool*/ y = /*@typeArgs=bool*/ f() && /*@typeArgs=bool*/ f();
+}
+
+main() {}