Support directories other than "web" in pub build.

sdk/lib/_internal/pub/test/build/warns_on_assets_paths_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.
 
 library pub_tests;
 
 import 'package:path/path.dart' as path;
 
 import '../../lib/src/utils.dart';
 import '../descriptor.dart' as d;
@@ skipping 14 matching lines @@
     d.dir(appPath, [
       d.appPubspec(),
       d.dir('web', [
         d.file('index.html'),
         d.dir('assets')
       ])
     ]).create();
 
     var assetsPath = path.join('web', 'assets');
     schedulePub(args: ['build'],
-        error: getWarningRegExp(assetsPath),
-        exitCode: 0);
+        error: getWarningRegExp(assetsPath));
   });
 
   integration('warns user about assets dir nested anywhere in "web"', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir('web', [
         d.file('index.html'),
         d.dir('foo', [
           d.dir('assets')
         ])
       ])
     ]).create();
 
     var assetsPath = path.join('web', 'foo', 'assets');
     schedulePub(args: ['build'],
-        error: getWarningRegExp(assetsPath),
-        exitCode: 0);
+        error: getWarningRegExp(assetsPath));
   });
 
   integration('warns user about assets file in the root of "web"', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir('web', [
         d.file('index.html'),
         d.file('assets')
       ])
     ]).create();
 
     var assetsPath = path.join('web', 'assets');
     schedulePub(args: ['build'],
-        error: getWarningRegExp(assetsPath),
-        exitCode: 0);
+        error: getWarningRegExp(assetsPath));
   });
 
   integration('warns user about assets file nested anywhere in "web"', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir('web', [
         d.file('index.html'),
         d.dir('foo', [
           d.file('assets')
         ])
       ])
     ]).create();
 
     var assetsPath = path.join('web', 'foo', 'assets');
     schedulePub(args: ['build'],
-        error: getWarningRegExp(assetsPath),
-        exitCode: 0);
+        error: getWarningRegExp(assetsPath));
   });
 
   integration('does not warn if no assets dir or file anywhere in "web"', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir('web', [
         d.file('index.html'),
         d.dir('foo')
       ])
     ]).create();
 
     schedulePub(args: ['build'],
         error: new RegExp(
-            r'^(?!Warning: Pub reserves paths containing "assets").*$'),
-        exitCode: 0);
+            r'^(?!Warning: Pub reserves paths containing "assets").*$'));
   });
 }