Add a flag to control the use of color in the test runner.

lib/src/util/io.dart

 // Copyright (c) 2015, 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.
 
 library unittest.util.io;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 15 matching lines @@
 // TODO(nweiz): Make this check [stdioType] once that works within "pub run".
 /// Whether "special" strings such as Unicode characters or color escapes are
 /// safe to use.
 ///
 /// On Windows or when not printing to a terminal, only printable ASCII
 /// characters should be used.
 bool get canUseSpecialChars =>
     Platform.operatingSystem != 'windows' &&
     Platform.environment["_UNITTEST_USE_COLOR"] != "false";
 
-/// Gets a "special" string (ANSI escape or Unicode).
-///
-/// On Windows or when not printing to a terminal, returns something else since
-/// those aren't supported.
-String getSpecial(String special, [String onWindows = '']) =>
-    canUseSpecialChars ? special : onWindows;
-
 /// Creates a temporary directory and passes its path to [fn].
 ///
 /// Once the [Future] returned by [fn] completes, the temporary directory and
 /// all its contents are deleted. [fn] can also return `null`, in which case
 /// the temporary directory is deleted immediately afterwards.
 ///
 /// Returns a future that completes to the value that the future returned from
 /// [fn] completes to.
 Future withTempDir(Future fn(String path)) {
   return new Future.sync(() {
@@ skipping 14 matching lines @@
   }
 
   // IPv6 addresses in URLs need to be enclosed in square brackets to avoid
   // URL ambiguity with the ":" in the address.
   if (address.type == InternetAddressType.IP_V6) {
     return new Uri(scheme: "http", host: "[${address.address}]", port: port);
   }
 
   return new Uri(scheme: "http", host: address.address, port: port);
 }