Make servePackages's contents argument saner.

sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart

Index: sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart
diff --git a/sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart b/sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart
index a084aa79a658f3177f87eeefc2424c369a1468a5..35bfa0d7e5b2fc82f6905b72edb32e0ab745c06e 100644
--- a/sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart
+++ b/sdk/lib/_internal/pub/test/snapshot/creates_a_snapshot_for_immediate_and_transitive_dep_test.dart
@@ -14,19 +14,21 @@ main() {
   initConfig();
   integration("creates a snapshot for an immediate dependency that's also a "
       "transitive dependency", () {
-    servePackages([
-      packageMap("foo", "1.2.3"),
-      packageMap("bar", "1.2.3", {"foo": "1.2.3"})
-    ], contents: [
-      d.dir("bin", [
-        d.file("hello.dart", "void main() => print('hello!');"),
-        d.file("goodbye.dart", "void main() => print('goodbye!');"),
-        d.file("shell.sh", "echo shell"),
-        d.dir("subdir", [
-          d.file("sub.dart", "void main() => print('sub!');")
+    servePackages((builder) {
+      builder.serve("foo", "1.2.3", contents: [
+        d.dir("bin", [
+          d.file("hello.dart", "void main() => print('hello!');"),
+          d.file("goodbye.dart", "void main() => print('goodbye!');"),
+          d.file("shell.sh", "echo shell"),
+          d.dir("subdir", [
+            d.file("sub.dart", "void main() => print('sub!');")
+          ])
         ])
-      ])
-    ]);
+      ]);
+      builder.serve("bar", "1.2.3", pubspec: {
+        "dependencies": {"foo": "1.2.3"}
+      });
+    });
 
     d.appDir({"foo": "1.2.3"}).create();