Drop support for older Barback versions.

test/dart2js/compiles_generated_file_from_dependency_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.
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 main() {
-  withBarbackVersions("any", () {
-    integration("compiles a Dart file that imports a generated file in another "
-                "package to JS", () {
-      d.dir("foo", [
-        d.pubspec({
-          "name": "foo",
-          "version": "0.0.1",
-          "transformers": ["foo/transformer"]
-        }),
-        d.dir("lib", [
-          d.file("foo.dart", """
+  integration("compiles a Dart file that imports a generated file in another "
+              "package to JS", () {
+    d.dir("foo", [
+      d.pubspec({
+        "name": "foo",
+        "version": "0.0.1",
+        "transformers": ["foo/transformer"]
+      }),
+      d.dir("lib", [
+        d.file("foo.dart", """
 library foo;
 const TOKEN = "before";
 foo() => TOKEN;
 """),
-          d.file("transformer.dart", dartTransformer("munge"))
-        ])
-      ]).create();
+        d.file("transformer.dart", dartTransformer("munge"))
+      ])
+    ]).create();
 
-      d.dir(appPath, [
-        d.appPubspec({
-          "foo": {
-            "path": "../foo"
-          }
-        }),
-        d.dir("web", [
-          d.file("main.dart", """
+    d.dir(appPath, [
+      d.appPubspec({
+        "foo": {
+          "path": "../foo"
+        }
+      }),
+      d.dir("web", [
+        d.file("main.dart", """
 import "package:foo/foo.dart";
 main() => print(foo());
 """)
-        ])
-      ]).create();
+      ])
+    ]).create();
 
-      createLockFile("myapp", sandbox: ["foo"], pkg: ["barback"]);
+    createLockFile("myapp", sandbox: ["foo"], pkg: ["barback"]);
 
-      pubServe();
-      requestShouldSucceed("main.dart.js", contains("(before, munge)"));
-      endPubServe();
-    });
+    pubServe();
+    requestShouldSucceed("main.dart.js", contains("(before, munge)"));
+    endPubServe();
   });
 }