Move common streams in barback to their own class.

pkg/barback/lib/src/node_streams.dart

Index: pkg/barback/lib/src/node_streams.dart
diff --git a/pkg/barback/lib/src/node_streams.dart b/pkg/barback/lib/src/node_streams.dart
new file mode 100644
index 0000000000000000000000000000000000000000..7b6632fae28503580b68cbc311ec1e3d2ce1813a
--- /dev/null
+++ b/pkg/barback/lib/src/node_streams.dart
@@ -0,0 +1,49 @@
+// 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.
+
+library barback.node_streams;
+
+import 'dart:async';
+
+import 'asset_node.dart';
+import 'log.dart';
+import 'stream_pool.dart';
+
+/// A collection of streams that are common to nodes in barback's package graph.
+class NodeStreams {
+  /// A stream that emits an event whenever the node is no longer dirty.
+  ///
+  /// This is synchronous in order to guarantee that it will emit an event as
+  /// soon as [isDirty] flips from `true` to `false`.
+  Stream get onDone => onDoneController.stream;
+  final onDoneController = new StreamController.broadcast(sync: true);
+
+  /// A stream that emits any new assets produced by the node.
+  ///
+  /// Assets are emitted synchronously to ensure that any changes are thoroughly
+  /// propagated as soon as they occur.
+  Stream<AssetNode> get onAsset => onAssetPool.stream;
+  final onAssetPool = new StreamPool<AssetNode>.broadcast();
+  final onAssetController =
+      new StreamController<AssetNode>.broadcast(sync: true);
+
+  /// A stream that emits an event whenever any the node logs an entry.
+  Stream<LogEntry> get onLog => onLogPool.stream;
+  final onLogPool = new StreamPool<LogEntry>.broadcast();
+  final onLogController = new StreamController<LogEntry>.broadcast(sync: true);
+
+  NodeStreams() {
+    onAssetPool.add(onAssetController.stream);
+    onLogPool.add(onLogController.stream);
+  }
+
+  /// Closes all the streams.
+  void close() {
+    onDoneController.close();
+    onAssetController.close();
+    onAssetPool.close();
+    onLogController.close();
+    onLogPool.close();
+  }
+}