Add a filesystem descriptor library to scheduled_test.

pkg/scheduled_test/lib/src/utils.dart

 // Copyright (c) 2013, 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 utils;
 
 import 'dart:async';
 
 /// Configures [future] so that its result (success or exception) is passed on
 /// to [completer].
 void chainToCompleter(Future future, Completer completer) {
   future.then((value) => completer.complete(value),
       onError: (e) => completer.completeError(e.error, e.stackTrace));
 }
 
 /// Prepends each line in [text] with [prefix].
 String prefixLines(String text, {String prefix: '| '}) =>
   text.split('\n').map((line) => '$prefix$line').join('\n');
 
 /// Returns a [Future] that completes after pumping the event queue [times]
 /// times. By default, this should pump the event queue enough times to allow
 /// any code to run, as long as it's not waiting on some external event.
 Future pumpEventQueue([int times=200]) {
   if (times == 0) return new Future.immediate(null);
   return new Future.immediate(null).then((_) => pumpEventQueue(times - 1));
 }
+
+/// Returns whether [iterable1] has the same elements in the same order as
+/// [iterable2]. The elements are compared using `==`.
+bool orderedIterableEquals(Iterable iterable1, Iterable iterable2) {
+  var iter1 = iterable1.iterator;
+  var iter2 = iterable2.iterator;
+
+  while (true) {
+    var hasNext1 = iter1.moveNext();
+    var hasNext2 = iter2.moveNext();
+    if (hasNext1 != hasNext2) return false;
+    if (!hasNext1) return true;
+    if (iter1.current != iter2.current) return false;
+  }
+}
+
+// TODO(nweiz): remove this when issue 8731 is fixed.
+/// Returns a [Stream] that will immediately emit [error] and then close.
+Stream errorStream(error) => new Future.immediateError(error).asStream();
+
+/// Returns a buffered stream that will emit the same values as the stream
+/// returned by [future] once [future] completes. If [future] completes to an
+/// error, the return value will emit that error and then close.
+Stream futureStream(Future<Stream> future) {
+  var controller = new StreamController();
+  future.then((stream) {
+    stream.listen(
+        controller.add,
+        onError: (error) => controller.signalError(error),
+        onDone: controller.close);
+  }).catchError((e) {
+    controller.signalError(e);
+    controller.close();
+  });
+  return controller.stream;
+}