Install barback from a hosted source in all tests.

test/dart2js/output_can_be_consumed_by_successive_phases.dart

Index: test/dart2js/output_can_be_consumed_by_successive_phases.dart
diff --git a/test/dart2js/output_can_be_consumed_by_successive_phases.dart b/test/dart2js/output_can_be_consumed_by_successive_phases.dart
index 2c5f9994e9a6b564f50bb713fa263a151d39a454..d1d5b9656dfda0676adf88aa92cd2c3a075a0864 100644
--- a/test/dart2js/output_can_be_consumed_by_successive_phases.dart
+++ b/test/dart2js/output_can_be_consumed_by_successive_phases.dart
@@ -28,10 +28,13 @@ class RewriteTransformer extends Transformer {
 
 main() {
   integration("output can be consumed by successive phases", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["\$dart2js", "myapp/src/transformer"]
+        "transformers": ["\$dart2js", "myapp/src/transformer"],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [d.dir("src", [
         d.file("transformer.dart", JS_REWRITE_TRANSFORMER)
@@ -39,8 +42,6 @@ main() {
       d.dir("web", [d.file("main.dart", "void main() {}")])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
     pubGet();
     pubServe();
     requestShouldSucceed("main.dart.out", isUnminifiedDart2JSOutput);