Install barback from a hosted source in all tests.

test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart

Index: test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart
diff --git a/test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart b/test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart
index dc6b94759ed68699a50937aa8601b41461782e2b..422bf32061d43c6fa6d3ce6c41b41f69f99f3dd3 100644
--- a/test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart
+++ b/test/dart2js/compiles_generated_file_from_dependency_outside_web_test.dart
@@ -12,11 +12,14 @@ main() {
   // This is a regression test for issue #17198.
   integration("compiles a Dart file that imports a generated file to JS "
       "outside web/", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "version": "0.0.1",
-        "transformers": ["myapp/transformer"]
+        "transformers": ["myapp/transformer"],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [
         d.file("transformer.dart", dartTransformer("munge"))
@@ -30,11 +33,10 @@ void main() => print(TOKEN);
 library other;
 const TOKEN = "before";
 """)
-        ])
+      ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     pubServe(args: ["test"]);
     requestShouldSucceed("main.dart.js", contains("(before, munge)"),
         root: "test");