Migrated test block 29 to Dart 2.0

tests/corelib_strong/string_trim_test.dart

-// Copyright (c) 2011, 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";
-
-class StringTrimTest {
-  static testMain() {
-    Expect.equals("", " ".trim());
-    Expect.equals("", "     ".trim());
-    var a = "      lots of space on the left";
-    Expect.equals("lots of space on the left", a.trim());
-    a = "lots of space on the right           ";
-    Expect.equals("lots of space on the right", a.trim());
-    a = "         lots of space           ";
-    Expect.equals("lots of space", a.trim());
-    a = "  x  ";
-    Expect.equals("x", a.trim());
-    Expect.equals("", " \t \n \r ".trim());
-  }
-}
-
-main() {
-  StringTrimTest.testMain();
-}