Install barback from a hosted source in all tests.

test/transformer/loads_a_diamond_transformer_dependency_graph_test.dart

 // Copyright (c) 2013, 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 '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 main() {
    integration("loads a diamond transformer dependency graph", () {
+     serveBarback();
+
      d.dir("top", [
        d.pubspec({
          "name": "top",
          "version": "1.0.0"
        }),
        d.dir("lib", [
          d.file("transformer.dart", dartTransformer('top')),
        ])
      ]).create();
 
      d.dir("left", [
        d.pubspec({
          "name": "left",
          "version": "1.0.0",
          "transformers": ["top/transformer"],
-         "dependencies": {"top": {"path": "../top"}}
+         "dependencies": {
+           "top": {"path": "../top"},
+           "barback": "any"
+         }
        }),
        d.dir("lib", [
          d.file("transformer.dart", dartTransformer('left')),
        ])
      ]).create();
 
      d.dir("right", [
        d.pubspec({
          "name": "right",
          "version": "1.0.0",
          "transformers": ["top/transformer"],
-         "dependencies": {"top": {"path": "../top"}}
+         "dependencies": {
+           "top": {"path": "../top"},
+           "barback": "any"
+         }
        }),
        d.dir("lib", [
          d.file("transformer.dart", dartTransformer('right')),
        ])
      ]).create();
 
      d.dir(appPath, [
        d.pubspec({
          "name": "myapp",
          "transformers": [
            "left/transformer",
            "right/transformer",
            "myapp/transformer"
          ],
          "dependencies": {
            'left': {'path': '../left'},
            'right': {'path': '../right'},
+           'barback': 'any'
          }
        }),
        d.dir("lib", [
          d.file("transformer.dart", dartTransformer('myapp'))
        ]),
        d.dir("web", [
          d.file("main.dart", 'const TOKEN = "main.dart";')
        ])
      ]).create();
 
-     createLockFile('myapp',
-         sandbox: ['top', 'left', 'right'],
-         pkg: ['barback']);
-
+     pubGet();
      pubServe();
      requestShouldSucceed("main.dart",
          'const TOKEN = "(((main.dart, (left, top)), (right, top)), ((myapp, '
          '(left, top)), (right, top)))";');
      endPubServe();
    });
 }