Don't implicitly run "pub get".

test/dart2js/omits_source_map_in_release_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 '../descriptor.dart' as d;
 import '../test_pub.dart';
 
 main() {
   integration("omits source maps from a release build", () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir("web", [
         d.file("main.dart", "void main() => print('hello');")
       ])
     ]).create();
 
+    pubGet();
     schedulePub(args: ["build"],
         output: new RegExp(r'Built 1 file to "build".'),
         exitCode: 0);
 
     d.dir(appPath, [
       d.dir('build', [
         d.dir('web', [
           d.nothing('main.dart.js.map')
         ])
       ])
     ]).validate();
   });
 }