Remove barback from the repo.

pkg/barback/lib/src/log.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 barback.log;
-
-import 'package:source_span/source_span.dart';
-
-import 'asset/asset_id.dart';
-import 'errors.dart';
-
-/// The severity of a logged message.
-class LogLevel {
-  static const INFO = const LogLevel("Info");
-  static const FINE = const LogLevel("Fine");
-  static const WARNING = const LogLevel("Warning");
-  static const ERROR = const LogLevel("Error");
-
-  final String name;
-  const LogLevel(this.name);
-
-  String toString() => name;
-}
-
-/// One message logged during a transform.
-class LogEntry {
-  /// The transform that logged the message.
-  final TransformInfo transform;
-
-  /// The asset that the message is associated with.
-  final AssetId assetId;
-
-  final LogLevel level;
-  final String message;
-
-  /// The location that the message pertains to or null if not associated with
-  /// a [SourceSpan].
-  final SourceSpan span;
-
-  LogEntry(this.transform, this.assetId, this.level, this.message, this.span);
-}