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..596ee2477e5c1a03cd192e1a91d7a88d3130df2c 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
@@ -17,16 +17,18 @@ main() {
     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!');")
+    ], contents: {
+      'foo-1.2.3': [
+        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!');")
+          ])
         ])
-      ])
-    ]);
+      ]
+    });
 
     d.appDir({"foo": "1.2.3"}).create();