Remove barback from the repo.

sdk/lib/_internal/pub/test/dependency_computer/utils.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/scheduled_test.dart';
 
@@ skipping 78 matching lines @@
   for (var package in listDir(sandboxDir)) {
     if (!fileExists(p.join(package, 'pubspec.yaml'))) continue;
     var packageName = p.basename(package);
     packages[packageName] = new Package.load(
         packageName, package, systemCache.sources);
   }
 
   loadPackage(packageName) {
     if (packages.containsKey(packageName)) return;
     packages[packageName] = new Package.load(
-        packageName, p.join(pkgPath, packageName), systemCache.sources);
+        packageName, packagePath(packageName), systemCache.sources);
     for (var dep in packages[packageName].dependencies) {
       loadPackage(dep.name);
     }
   }
 
   loadPackage('barback');
 
   return new PackageGraph(entrypoint, null, packages);
 }
 
@@ skipping 10 matching lines @@
 
   buffer.writeln("""
 NoOpTransformer extends Transformer {
   bool isPrimary(AssetId id) => true;
   void apply(Transform transform) {}
 }
 """);
 
   return buffer.toString();
 }