Expose the Observatory URL when debugging.

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index e44e304d7435c43255ffc5d24111fd1cd94f210f..41211f335aff7ea90945d06b46c7e354799965c5 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -339,23 +339,28 @@ CancelableFuture cancelableNext(StreamQueue queue) {
   return completer.future;
 }
 
-/// Returns the result of whichever of [futures] completes first, and cancels
-/// the others.
-Future race(Iterable<CancelableFuture> futures) {
-  var completer = new Completer.sync();
-  for (var future in futures) {
-    future.then((value) {
-      if (!completer.isCompleted) completer.complete(value);
-    }).catchError((error, stackTrace) {
-      if (!completer.isCompleted) completer.completeError(error, stackTrace);
+/// Returns a single-subscription stream that emits the results of [futures] in
+/// the order they complete.
+///
+/// If any futures in [futures] are [CancelableFuture]s, this will cancel them
+/// if the subscription is canceled.
+Stream inCompletionOrder(Iterable<Future> futures) {
+  var futureSet = futures.toSet();
+  var controller = new StreamController(sync: true, onCancel: () {
+    return Future.wait(futureSet.map((future) {
+      return future is CancelableFuture ? future.cancel() : null;
+    }).where((future) => future != null));
+  });
+
+  for (var future in futureSet) {
+    future.then(controller.add).catchError(controller.addError)
+        .whenComplete(() {
+      futureSet.remove(future);
+      if (futureSet.isEmpty) controller.close();
     });
   }
 
-  return completer.future.whenComplete(() {
-    for (var future in futures) {
-      future.cancel();
-    }
-  });
+  return controller.stream;
 }
 
 /// Returns a stream that emits [error] and [stackTrace], then closes.