Make servePackages's contents argument saner.

sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart

Index: sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart
diff --git a/sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart b/sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart
index 47cdba66502f2de8e667f5b26380695ab9aa92f9..4218e768612e1f4a64d3acfaf7dc922c5509f078 100644
--- a/sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart
+++ b/sdk/lib/_internal/pub/test/get/hosted/resolve_constraints_test.dart
@@ -10,13 +10,17 @@ import '../../test_pub.dart';
 main() {
   initConfig();
   integration('resolves version constraints from a pub server', () {
-    servePackages([
-      packageMap("foo", "1.2.3", {"baz": ">=2.0.0"}),
-      packageMap("bar", "2.3.4", {"baz": "<3.0.0"}),
-      packageMap("baz", "2.0.3"),
-      packageMap("baz", "2.0.4"),
-      packageMap("baz", "3.0.1")
-    ]);
+    servePackages((builder) {
+      builder.serve("foo", "1.2.3", pubspec: {
+        "dependencies": {"baz": ">=2.0.0"}
+      });
+      builder.serve("bar", "2.3.4", pubspec: {
+        "dependencies": {"baz": "<3.0.0"}
+      });
+      builder.serve("baz", "2.0.3");
+      builder.serve("baz", "2.0.4");
+      builder.serve("baz", "3.0.1");
+    });
 
     d.appDir({"foo": "any", "bar": "any"}).create();