Make servePackages's contents argument saner.

sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart

Index: sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart
diff --git a/sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart b/sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart
index 7de2061948cd38c04a2e73685b69c062da600a85..76edd9834251d3b69228e19653553fe57b2b820e 100644
--- a/sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart
+++ b/sdk/lib/_internal/pub/test/upgrade/hosted/unlock_if_necessary_test.dart
@@ -11,10 +11,10 @@ main() {
   initConfig();
   integration("upgrades one locked pub server package's dependencies if it's "
       "necessary", () {
-    servePackages([
-      packageMap("foo", "1.0.0", {"foo_dep": "any"}),
-      packageMap("foo_dep", "1.0.0")
-    ]);
+    servePackages((builder) {
+      builder.serve("foo", "1.0.0", deps: {"foo_dep": "any"});
+      builder.serve("foo_dep", "1.0.0");
+    });
 
     d.appDir({"foo": "any"}).create();
 
@@ -25,10 +25,10 @@ main() {
       "foo_dep": "1.0.0"
     }).validate();
 
-    servePackages([
-      packageMap("foo", "2.0.0", {"foo_dep": ">1.0.0"}),
-      packageMap("foo_dep", "2.0.0")
-    ]);
+    servePackages((builder) {
+      builder.serve("foo", "2.0.0", deps: {"foo_dep": ">1.0.0"});
+      builder.serve("foo_dep", "2.0.0");
+    });
 
     pubUpgrade(args: ['foo']);