Reorganize barback's source files.

pkg/barback/lib/src/graph/node_streams.dart

 // 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;
+library barback.graph.node_streams;
 
 import 'dart:async';
 
-import 'asset_node.dart';
-import 'log.dart';
+import '../asset/asset_node.dart';
+import '../log.dart';
+import '../utils/stream_pool.dart';
 import 'node_status.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 every time the node's status changes.
   ///
   /// This will emit the new status. It's guaranteed to emit an event only when
   /// the status changes from the previous value. To ensure this, callers should
   /// emit status changes using [changeStatus]. The initial status is assumed to
   /// be [NodeStatus.RUNNING].
   Stream<NodeStatus> get onStatusChange => _onStatusChangeController.stream;
@@ skipping 34 matching lines @@
 
   /// Closes all the streams.
   void close() {
     _onStatusChangeController.close();
     onAssetController.close();
     onAssetPool.close();
     onLogController.close();
     onLogPool.close();
   }
 }