Don't load assets unnecessarily when precompiling executables.

sdk/lib/_internal/pub/test/deps_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
 
 main() {
   initConfig();
 
   setUp(() {
-    servePackages([
-      packageMap("normal", "1.2.3", {
+    servePackages((builder) {
+      builder.serve("normal", "1.2.3", deps: {
         "transitive": "any",
         "circular_a": "any"
-      }),
-      packageMap("transitive", "1.2.3", {
-        "shared": "any"
-      }),
-      packageMap("shared", "1.2.3", {
-        "other": "any"
-      }),
-      packageMap("unittest", "1.2.3", {
-        "shared": "any"
-      }),
-      packageMap("other", "1.0.0"),
-      packageMap("overridden", "1.0.0"),
-      packageMap("overridden", "2.0.0"),
-      packageMap("override_only", "1.2.3"),
-      packageMap("circular_a", "1.2.3", {
-        "circular_b": "any"
-      }),
-      packageMap("circular_b", "1.2.3", {
-        "circular_a": "any"
-      })
-    ]);
+      });
+      builder.serve("transitive", "1.2.3", deps: {"shared": "any"});
+      builder.serve("shared", "1.2.3", deps: {"other": "any"});
+      builder.serve("unittest", "1.2.3", deps: {"shared": "any"});
+      builder.serve("other", "1.0.0");
+      builder.serve("overridden", "1.0.0");
+      builder.serve("overridden", "2.0.0");
+      builder.serve("override_only", "1.2.3");
+      builder.serve("circular_a", "1.2.3", deps: {"circular_b": "any"});
+      builder.serve("circular_b", "1.2.3", deps: {"circular_a": "any"});
+    });
 
     d.dir("from_path", [
       d.libDir("from_path"),
       d.libPubspec("from_path", "1.2.3")
     ]).create();
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dependencies": {
@@ skipping 83 matching lines @@
         |   '-- transitive 1.2.3
         |       '-- shared...
         |-- overridden 2.0.0
         |-- override_only 1.2.3
         '-- unittest 1.2.3
             '-- shared 1.2.3
                 '-- other 1.0.0
         ''');
   });
 }