Add stack chain support to pub.

sdk/lib/_internal/pub/lib/src/barback/load_transformers.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 pub.load_transformers;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 
 import 'package:barback/barback.dart';
 // TODO(nweiz): don't import from "src" once issue 14966 is fixed.
 import 'package:barback/src/internal_asset.dart';
 import 'package:source_maps/source_maps.dart';
+import 'package:stack_trace/stack_trace.dart';
 
 import '../barback.dart';
 import '../dart.dart' as dart;
 import '../log.dart' as log;
 import '../utils.dart';
 import 'server.dart';
 
 /// A Dart script to run in an isolate.
 ///
 /// This script serializes one or more transformers defined in a Dart library
@@ skipping 510 matching lines @@
 Map _serializeId(AssetId id) => {'package': id.package, 'path': id.path};
 
 /// Responds to a message sent by [_call].
 ///
 /// [wrappedMessage] is the raw message sent by [_call]. This unwraps it and
 /// passes the contents of the message to [callback], then sends the return
 /// value of [callback] back to [_call]. If [callback] returns a Future or
 /// throws an error, that will also be sent.
 void _respond(wrappedMessage, callback(message)) {
   var replyTo = wrappedMessage['replyTo'];
-  new Future.sync(() => callback(wrappedMessage['message']))
+  syncFuture(() => callback(wrappedMessage['message']))
       .then((result) => replyTo.send({'type': 'success', 'value': result}))
       .catchError((error, stackTrace) {
     // TODO(nweiz): at least MissingInputException should be preserved here.
     replyTo.send({
       'type': 'error',
       'error': dart.CrossIsolateException.serialize(error, stackTrace)
     });
   });
 }
 
 /// Wraps [message] and sends it across [port], then waits for a response which
 /// should be sent using [_respond].
 ///
 /// The returned Future will complete to the value or error returned by
 /// [_respond].
 Future _call(SendPort port, message) {
   var receivePort = new ReceivePort();
   port.send({
     'message': message,
     'replyTo': receivePort.sendPort
   });
 
-  return receivePort.first.then((response) {
+  return Chain.track(receivePort.first).then((response) {
     if (response['type'] == 'success') return response['value'];
     assert(response['type'] == 'error');
     return new Future.error(
-        new dart.CrossIsolateException.deserialize(response['error']));
+        new dart.CrossIsolateException.deserialize(response['error']),
+        new Chain.current());
   });
 }