Make servePackages's contents argument saner.

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

Index: sdk/lib/_internal/pub/test/snapshot/snapshots_transformed_code_test.dart
diff --git a/sdk/lib/_internal/pub/test/snapshot/snapshots_transformed_code_test.dart b/sdk/lib/_internal/pub/test/snapshot/snapshots_transformed_code_test.dart
index 38018ced4ecaaabfe467081ff3ced612d9f65f12..601941f74b59fa661093d7cb12c2d1222945e0ed 100644
--- a/sdk/lib/_internal/pub/test/snapshot/snapshots_transformed_code_test.dart
+++ b/sdk/lib/_internal/pub/test/snapshot/snapshots_transformed_code_test.dart
@@ -35,16 +35,18 @@ main() {
     servePackages([
       packageMap("foo", "1.2.3", {"barback": "any"})
           ..addAll({'transformers': ['foo']})
-    ], contents: [
-      d.dir("lib", [d.file("foo.dart", REPLACE_TRANSFORMER)]),
-      d.dir("bin", [
-        d.file("hello.dart", """
+    ], contents: {
+      'foo-1.2.3': [
+        d.dir("lib", [d.file("foo.dart", REPLACE_TRANSFORMER)]),
+        d.dir("bin", [
+          d.file("hello.dart", """
 final message = 'REPLACE ME';
 
 void main() => print(message);
 """),
-      ])
-    ], serveBarback: true);
+        ])
+      ]
+    }, serveBarback: true);
 
     d.appDir({"foo": "1.2.3"}).create();