Revise barback logging patch.

pkg/barback/lib/src/phase.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.phase;
 
 import 'dart:async';
-import 'dart:collection';
 
 import 'asset_cascade.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
-import 'asset_set.dart';
-import 'barback_logger.dart';
 import 'group_runner.dart';
-import 'errors.dart';
+import 'log.dart';
 import 'multiset.dart';
 import 'phase_forwarder.dart';
 import 'phase_input.dart';
 import 'phase_output.dart';
 import 'stream_pool.dart';
 import 'transformer.dart';
 import 'transformer_group.dart';
 import 'utils.dart';
 
 /// One phase in the ordered series of transformations in an [AssetCascade].
@@ skipping 58 matching lines @@
 
   /// A controller whose stream feeds into [_onDirtyPool].
   ///
   /// This is used whenever an input is added or transforms are changed.
   final _onDirtyController = new StreamController.broadcast(sync: true);
 
   /// Whether this phase is dirty and needs to be run.
   bool get isDirty => _inputs.values.any((input) => input.isDirty) ||
       _groups.values.any((group) => group.isDirty);
 
-  /// A stream that emits an event whenever any transforms in this phase log an
-  /// entry.
+  /// A stream that emits an event whenever any transforms in this phase logs
+  /// an entry.
   Stream<LogEntry> get onLog => _onLogPool.stream;
   final _onLogPool = new StreamPool<LogEntry>.broadcast();
 
   /// The phase after this one.
   ///
   /// Outputs from this phase will be passed to it.
   Phase get next => _next;
   Phase _next;
 
   /// Returns all currently-available output assets for this phase.
@@ skipping 199 matching lines @@
       _outputs[asset.id].add(asset);
     } else {
       _outputs[asset.id] = new PhaseOutput(this, asset);
       _outputs[asset.id].onAsset.listen((output) {
         if (_next != null) _next.addInput(output);
       }, onDone: () => _outputs.remove(asset.id));
       if (_next != null) _next.addInput(_outputs[asset.id].output);
     }
   }
 }