Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/asset/dart/utils.dart

Index: sdk/lib/_internal/pub_generated/asset/dart/utils.dart
diff --git a/sdk/lib/_internal/pub_generated/asset/dart/utils.dart b/sdk/lib/_internal/pub_generated/asset/dart/utils.dart
deleted file mode 100644
index 72150edf0b17f2d4b8070558bec91102f8d60999..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/asset/dart/utils.dart
+++ /dev/null
@@ -1,86 +0,0 @@
-// Copyright (c) 2014, 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.
-
-/// Functions go in this file as opposed to lib/src/utils.dart if they need to
-/// be accessible to the transformer-loading isolate.
-library pub.asset.utils;
-
-import 'dart:async';
-
-/// A regular expression to match the exception prefix that some exceptions'
-/// [Object.toString] values contain.
-final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');
-
-/// Get a string description of an exception.
-///
-/// Many exceptions include the exception class name at the beginning of their
-/// [toString], so we remove that if it exists.
-String getErrorMessage(error) =>
-  error.toString().replaceFirst(_exceptionPrefix, '');
-
-/// 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.
-///
-/// If [broadcast] is true, a broadcast stream is returned. This assumes that
-/// the stream returned by [future] will be a broadcast stream as well.
-/// [broadcast] defaults to false.
-Stream futureStream(Future<Stream> future, {bool broadcast: false}) {
-  var subscription;
-  var controller;
-
-  future = future.catchError((e, stackTrace) {
-    // Since [controller] is synchronous, it's likely that emitting an error
-    // will cause it to be cancelled before we call close.
-    if (controller != null) controller.addError(e, stackTrace);
-    if (controller != null) controller.close();
-    controller = null;
-  });
-
-  onListen() {
-    future.then((stream) {
-      if (controller == null) return;
-      subscription = stream.listen(
-          controller.add,
-          onError: controller.addError,
-          onDone: controller.close);
-    });
-  }
-
-  onCancel() {
-    if (subscription != null) subscription.cancel();
-    subscription = null;
-    controller = null;
-  }
-
-  if (broadcast) {
-    controller = new StreamController.broadcast(
-        sync: true, onListen: onListen, onCancel: onCancel);
-  } else {
-    controller = new StreamController(
-        sync: true, onListen: onListen, onCancel: onCancel);
-  }
-  return controller.stream;
-}
-
-/// Returns a [Stream] that will emit the same values as the stream returned by
-/// [callback].
-///
-/// [callback] will only be called when the returned [Stream] gets a subscriber.
-Stream callbackStream(Stream callback()) {
-  var subscription;
-  var controller;
-  controller = new StreamController(onListen: () {
-    subscription = callback().listen(controller.add,
-        onError: controller.addError,
-        onDone: controller.close);
-  },
-      onCancel: () => subscription.cancel(),
-      onPause: () => subscription.pause(),
-      onResume: () => subscription.resume(),
-      sync: true);
-  return controller.stream;
-}