Auto-run "pub get" more for "pub run".

test/run/forwards_signal_posix_test.dart

 // Copyright (c) 2015, 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.
 
 // Windows doesn't support sending signals.
 @TestOn('!windows')
 
 import 'dart:io';
 
 import '../descriptor.dart' as d;
@@ skipping 23 matching lines @@
 
 main() {
   integration('forwards signals to the inner script', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir("bin", [
         d.file("script.dart", SCRIPT)
       ])
     ]).create();
 
-    var pub = pubRun(args: ["bin/script"]);
+    var pub = pubRun(args: ["bin/script"], shouldGetFirst: true);
 
     pub.stdout.expect("ready");
     for (var signal in _catchableSignals) {
       pub.signal(signal);
       pub.stdout.expect(signal.toString());
     }
 
     pub.kill();
   });
 }