Make servePackages's contents argument saner.

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

Index: sdk/lib/_internal/pub/test/snapshot/doesnt_snapshot_transitive_dependencies_test.dart
diff --git a/sdk/lib/_internal/pub/test/snapshot/doesnt_snapshot_transitive_dependencies_test.dart b/sdk/lib/_internal/pub/test/snapshot/doesnt_snapshot_transitive_dependencies_test.dart
index 9b4512e7f9666be7ea99f86a86a4e129829e725a..8eec70e6859c2d81f13e890b787ae653bdb41f3d 100644
--- a/sdk/lib/_internal/pub/test/snapshot/doesnt_snapshot_transitive_dependencies_test.dart
+++ b/sdk/lib/_internal/pub/test/snapshot/doesnt_snapshot_transitive_dependencies_test.dart
@@ -14,12 +14,14 @@ main() {
   initConfig();
   integration("doesn't create a snapshot for transitive dependencies' "
       "executables", () {
-    servePackages([
-      packageMap("foo", "1.2.3", {'bar': '1.2.3'}),
-      packageMap("bar", "1.2.3")
-    ], contents: [
-      d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])
-    ]);
+    servePackages((builder) {
+      builder.serve("foo", "1.2.3", pubspec: {
+        "dependencies": {'bar': '1.2.3'}
+      });
+      builder.serve("bar", "1.2.3", contents: [
+        d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])
+      ]);
+    });
 
     d.appDir({"foo": "1.2.3"}).create();