Drop support for older Barback versions.

test/build/defaults_to_release_mode_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';
 
 const TRANSFORMER = """
@@ skipping 10 matching lines @@
   Future apply(Transform transform) {
     return new Future.value().then((_) {
       var id = transform.primaryInput.id.changeExtension(".out");
       transform.addOutput(new Asset.fromString(id, settings.mode.toString()));
     });
   }
 }
 """;
 
 main() {
-  withBarbackVersions("any", () {
-    integration("defaults to release mode", () {
-      d.dir(appPath, [
-        d.pubspec({
-          "name": "myapp",
-          "transformers": ["myapp/src/transformer"]
-        }),
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", TRANSFORMER)
-        ])]),
-        d.dir("web", [
-          d.file("foo.txt", "foo")
-        ])
-      ]).create();
+   integration("defaults to release mode", () {
+     d.dir(appPath, [
+       d.pubspec({
+         "name": "myapp",
+         "transformers": ["myapp/src/transformer"]
+       }),
+       d.dir("lib", [d.dir("src", [
+         d.file("transformer.dart", TRANSFORMER)
+       ])]),
+       d.dir("web", [
+         d.file("foo.txt", "foo")
+       ])
+     ]).create();
 
-      createLockFile('myapp', pkg: ['barback']);
+     createLockFile('myapp', pkg: ['barback']);
 
-      schedulePub(args: ["build"]);
+     schedulePub(args: ["build"]);
 
-      d.dir(appPath, [
-        d.dir('build', [
-          d.dir('web', [
-            d.file('foo.out', 'release')
-          ])
-        ])
-      ]).validate();
-    });
-  });
+     d.dir(appPath, [
+       d.dir('build', [
+         d.dir('web', [
+           d.file('foo.out', 'release')
+         ])
+       ])
+     ]).validate();
+   });
 }