Fix a barback bug where a result could be emitted incorrectly.

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 'package:barback/src/utils.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../utils.dart';
@@ skipping 984 matching lines @@
       updateSources(["pkg1|a.txt", "pkg2|a.txt"]);
       expectAsset("pkg1|a.out", "a.inc");
       buildShouldSucceed();
 
       modifyAsset("pkg2|a.txt", "new a");
       updateSources(["pkg2|a.txt"]);
       expectAsset("pkg1|a.out", "new a.inc");
       buildShouldSucceed();
     });
 
+    test("doesn't complete the build until all packages' transforms are "
+        "finished running", () {
+      var transformer = new ManyToOneTransformer("txt");
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {
+        "pkg1": [[transformer]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a");
+      buildShouldSucceed();
+
+      transformer.pauseApply();
+      modifyAsset("pkg2|a.inc", "new a");
+      updateSources(["pkg2|a.inc"]);
+      buildShouldNotBeDone();
+
+      transformer.resumeApply();
+      buildShouldSucceed();
+    });
+
     test("runs a transform that's added because of a change in another package",
         () {
       initGraph({
         "pkg1|a.txt": "pkg2|a.inc",
         "pkg2|a.inc": "b"
       }, {
         "pkg1": [
           [new ManyToOneTransformer("txt")],
           [new OneToManyTransformer("out")],
           [new RewriteTransformer("md", "done")]
@@ skipping 108 matching lines @@
       transformer1.resumeApply();
 
       expectAsset("app|foo.out", "foo.mid.out");
       buildShouldSucceed();
 
       expect(transformer1.numRuns, completion(equals(2)));
       expect(transformer2.numRuns, completion(equals(2)));
     });
   });
 }