Move a bunch of src/ files into subdirectories.

lib/src/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.io;
-
-import 'dart:async';
-import 'dart:io';
-
-import 'package:path/path.dart' as p;
-
-/// Returns whether the current Dart version supports [Isolate.kill].
-final bool supportsIsolateKill = _supportsIsolateKill;
-bool get _supportsIsolateKill {
-  // This isn't 100% accurate, since early 1.9 dev releases didn't support
-  // Isolate.kill(), but it's very unlikely anyone will be using them.
-  // TODO(nweiz): remove this when we no longer support older Dart versions.
-  var path = p.join(p.dirname(p.dirname(Platform.executable)), 'version');
-  return new File(path).readAsStringSync().startsWith('1.9');
-}
-
-// 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(() {
-    // TODO(nweiz): Empirically test whether sync or async functions perform
-    // better here when starting a bunch of isolates.
-    var tempDir = Directory.systemTemp.createTempSync('unittest_');
-    return new Future.sync(() => fn(tempDir.path))
-        .whenComplete(() => tempDir.deleteSync(recursive: true));
-  });
-}