Fix a bunch of pub tests that started running "pub get".

test/dart2js/environment_constant_test.dart

 // Copyright (c) 2014, 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.
 
 // Dart2js can take a long time to compile dart code, so we increase the timeout
 // to cope with that.
 @Timeout.factor(3)
 
 import 'package:scheduled_test/scheduled_test.dart';
 
@@ skipping 20 matching lines @@
       d.dir(appPath, [
         d.dir('build', [
           d.dir('web', [
             d.matcherFile('file.dart.js', contains('fblthp')),
           ])
         ])
       ]).validate();
     });
 
     integration('from "pub serve"', () {
-      pubServe(args: ["--define", "name=fblthp"]);
+      pubServe(args: ["--define", "name=fblthp"], shouldGetFirst: true);
       requestShouldSucceed("file.dart.js", contains("fblthp"));
       endPubServe();
     });
 
     integration('which takes precedence over the pubspec', () {
       d.dir(appPath, [
         d.pubspec({
           "name": "myapp",
           "transformers": [
             {"\$dart2js": {"environment": {"name": "slartibartfast"}}}
           ]
         })
       ]).create();
 
-      pubServe(args: ["--define", "name=fblthp"]);
+      pubServe(args: ["--define", "name=fblthp"], shouldGetFirst: true);
       requestShouldSucceed("file.dart.js", allOf([
         contains("fblthp"),
         isNot(contains("slartibartfast"))
       ]));
       endPubServe();
     });
   });
 }