Support configuring dart2js from the pubspec.

sdk/lib/_internal/pub/test/transformer/dart2js/output_can_be_consumed_by_successive_phases.dart

Index: sdk/lib/_internal/pub/test/transformer/dart2js/output_can_be_consumed_by_successive_phases.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/configuration/configuration_defaults_to_empty_map_test.dart b/sdk/lib/_internal/pub/test/transformer/dart2js/output_can_be_consumed_by_successive_phases.dart
similarity index 51%
copy from sdk/lib/_internal/pub/test/transformer/configuration/configuration_defaults_to_empty_map_test.dart
copy to sdk/lib/_internal/pub/test/transformer/dart2js/output_can_be_consumed_by_successive_phases.dart
index 1d8a1cf6b35c049e043bc953948e1e0b814ae414..4bdd6943f6b16ccee79ae26f9723791e55fc84f4 100644
--- a/sdk/lib/_internal/pub/test/transformer/configuration/configuration_defaults_to_empty_map_test.dart
+++ b/sdk/lib/_internal/pub/test/transformer/dart2js/output_can_be_consumed_by_successive_phases.dart
@@ -4,30 +4,27 @@
 
 library pub_tests;
 
-import 'dart:convert';
+import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 import '../../serve/utils.dart';
 
-final transformer = """
+/// The code for a transformer that renames ".js" files to ".out".
+const JS_REWRITE_TRANSFORMER = """
 import 'dart:async';
-import 'dart:convert';
 
 import 'package:barback/barback.dart';
 
-class ConfigTransformer extends Transformer {
-  final BarbackSettings settings;
+class RewriteTransformer extends Transformer {
+  RewriteTransformer.asPlugin();
 
-  ConfigTransformer.asPlugin(this.settings);
-
-  String get allowedExtensions => '.txt';
+  String get allowedExtensions => '.js';
 
   Future apply(Transform transform) {
     return transform.primaryInput.readAsString().then((contents) {
-      var id = transform.primaryInput.id.changeExtension(".json");
-      transform.addOutput(
-          new Asset.fromString(id, JSON.encode(settings.configuration)));
+      var id = transform.primaryInput.id.changeExtension(".out");
+      transform.addOutput(new Asset.fromString(id, contents));
     });
   }
 }
@@ -35,24 +32,23 @@ class ConfigTransformer extends Transformer {
 
 main() {
   initConfig();
-  integration("configuration defaults to an empty map", () {
+
+  integration("output can be consumed by successive phases", () {
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["myapp/src/transformer"]
+        "transformers": ["\$dart2js", "myapp/src/transformer"]
       }),
       d.dir("lib", [d.dir("src", [
-        d.file("transformer.dart", transformer)
+        d.file("transformer.dart", JS_REWRITE_TRANSFORMER)
       ])]),
-      d.dir("web", [
-        d.file("foo.txt", "foo")
-      ])
+      d.dir("web", [d.file("main.dart", "void main() {}")])
     ]).create();
 
     createLockFile('myapp', pkg: ['barback']);
 
-    var server = pubServe();
-    requestShouldSucceed("foo.json", JSON.encode({}));
+    pubServe();
+    requestShouldSucceed("main.dart.out", isUnminifiedDart2JSOutput);
     endPubServe();
   });
 }