Drop support for older Barback versions.

test/transformer/exclusion/works_on_dart2js_test.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:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 import '../../serve/utils.dart';
 
 main() {
-  withBarbackVersions("any", () {
-    integration("works on the dart2js transformer", () {
-      d.dir(appPath, [
-        d.pubspec({
-          "name": "myapp",
-          "transformers": [
-            {
-              "\$dart2js": {
-                "\$include": ["web/a.dart", "web/b.dart"],
-                "\$exclude": "web/a.dart"
-              }
+  integration("works on the dart2js transformer", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": [
+          {
+            "\$dart2js": {
+              "\$include": ["web/a.dart", "web/b.dart"],
+              "\$exclude": "web/a.dart"
             }
-          ]
-        }),
-        d.dir("web", [
-          d.file("a.dart", "void main() => print('hello');"),
-          d.file("b.dart", "void main() => print('hello');"),
-          d.file("c.dart", "void main() => print('hello');")
-        ])
-      ]).create();
+          }
+        ]
+      }),
+      d.dir("web", [
+        d.file("a.dart", "void main() => print('hello');"),
+        d.file("b.dart", "void main() => print('hello');"),
+        d.file("c.dart", "void main() => print('hello');")
+      ])
+    ]).create();
 
-      createLockFile('myapp', pkg: ['barback']);
+    createLockFile('myapp', pkg: ['barback']);
 
-      var server = pubServe();
-      // Dart2js should remain lazy.
-      server.stdout.expect("Build completed successfully");
+    var server = pubServe();
+    // Dart2js should remain lazy.
+    server.stdout.expect("Build completed successfully");
 
-      requestShould404("a.dart.js");
-      requestShouldSucceed("b.dart.js", isNot(isEmpty));
-      server.stdout.expect(consumeThrough(emitsLines(
-          "[Info from Dart2JS]:\n"
-          "Compiling myapp|web/b.dart...")));
-      server.stdout.expect(consumeThrough("Build completed successfully"));
+    requestShould404("a.dart.js");
+    requestShouldSucceed("b.dart.js", isNot(isEmpty));
+    server.stdout.expect(consumeThrough(emitsLines(
+        "[Info from Dart2JS]:\n"
+        "Compiling myapp|web/b.dart...")));
+    server.stdout.expect(consumeThrough("Build completed successfully"));
 
-      requestShould404("c.dart.js");
-      endPubServe();
-    });
+    requestShould404("c.dart.js");
+    endPubServe();
   });
 }