Make servePackages's contents argument saner.

sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart

Index: sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart
diff --git a/sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart b/sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart
index 54d2e946c1e59b2ec8003f5b53537d5f0c1039b6..6f9e009bf1d2e1d52a6e14012735f459f8dc6bf8 100644
--- a/sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart
+++ b/sdk/lib/_internal/pub/test/cache/repair/handles_failure_test.dart
@@ -14,10 +14,10 @@ main() {
   initConfig();
   integration('handles failure to reinstall some packages', () {
     // Only serve two packages so repairing will have a failure.
-    servePackages([
-      packageMap("foo", "1.2.3"),
-      packageMap("foo", "1.2.5")
-    ]);
+    servePackages((builder) {
+      builder.serve("foo", "1.2.3");
+      builder.serve("foo", "1.2.5");
+    });
 
     // Set up a cache with some packages.
     d.dir(cachePath, [