Fix a pass-through bug 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.package_graph.transform_test;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/utils.dart';
@@ skipping 901 matching lines @@
 
       updateSources(["app|foo.in"]);
       expectAsset("app|foo.mid", "foo.mid.phase3");
       buildShouldSucceed();
 
       modifyAsset("app|foo.in", "bar");
       updateSources(["app|foo.in"]);
       expectAsset("app|foo.mid", "bar.mid.phase2");
       buildShouldSucceed();
     });
+
+    test("doesn't pass an asset through if it's removed during isPrimary", () {
+      var check = new CheckContentTransformer("bar", " modified");
+      initGraph(["app|foo.txt"], {"app": [[check]]});
+
+      updateSources(["app|foo.txt"]);
+      expectAsset("app|foo.txt", "foo");
+      buildShouldSucceed();
+
+      check.pauseIsPrimary("app|foo.txt");
+      modifyAsset("app|foo.txt", "bar");
+      updateSources(["app|foo.txt"]);
+      // Ensure we're waiting on [check.isPrimary]
+      schedule(pumpEventQueue);
+
+      removeSources(["app|foo.txt"]);
+      check.resumeIsPrimary("app|foo.txt");
+      expectNoAsset("app|foo.txt");
+      buildShouldSucceed();
+    });
   });
 
   group('cross-package transforms', () {
     test("can access other packages' source assets", () {
       initGraph({
         "pkg1|a.txt": "pkg2|a.inc",
         "pkg2|a.inc": "a"
       }, {"pkg1": [[new ManyToOneTransformer("txt")]]});
 
       updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
@@ skipping 101 matching lines @@
       buildShouldSucceed();
 
       modifyAsset("pkg2|a.inc", "b");
       updateSources(["pkg2|a.inc"]);
       expectAsset("pkg1|b", "spread out");
       expectNoAsset("pkg1|c.done");
       buildShouldSucceed();
     });
   });
 }