Rename several classes in barback.

pkg/barback/test/package_graph/transform_test.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.test.asset_graph.transform_test;
+library barback.test.package_graph.transform_test;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
-import 'package:barback/src/asset_graph.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../utils.dart';
 
 main() {
   initConfig();
   test("gets a transformed asset with a different path", () {
     initGraph(["app|foo.blub"], {"app": [
       [new RewriteTransformer("blub", "blab")]
     ]});
@@ skipping 381 matching lines @@
     schedule(() => updateSources(["pkg2|foo.txt"]));
     expectAsset("pkg1|foo.out", "foo.out");
     buildShouldNotBeDone();
 
     // Now that the provider is unpaused, pkg2's transforms finish and the
     // overall build succeeds.
     resumeProvider();
     buildShouldSucceed();
   });
 }