Support directories other than "web" in pub build.

sdk/lib/_internal/pub/test/build/compiles_entrypoints_in_test_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.
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+main() {
+  initConfig();
+
+  integration("compiles Dart entrypoints in test/ to JS", () {
+    // Dart2js can take a long time to compile dart code, so we increase the
+    // timeout to cope with that.
+    currentSchedule.timeout *= 3;
+
+    d.dir(appPath, [
+      d.appPubspec(),
+      d.dir('test', [
+        d.file('file.dart', 'void main() => print("hello");'),
+        d.file('lib.dart', 'void foo() => print("hello");'),
+        d.dir('subdir', [
+          d.file('subfile.dart', 'void main() => print("ping");')
+        ])
+      ])
+    ]).create();
+
+    schedulePub(args: ["build", "test"],
+        output: new RegExp(r"Built 6 files!"));
+
+    d.dir(appPath, [
+      d.dir('build', [
+        d.dir('test', [
+          d.matcherFile('file.dart.js', isNot(isEmpty)),
+          d.matcherFile('file.dart.precompiled.js', isNot(isEmpty)),
+          d.matcherFile('file.dart.js.map', isNot(isEmpty)),
+          d.nothing('file.dart'),
+          d.nothing('lib.dart'),
+          d.dir('subdir', [
+            d.matcherFile('subfile.dart.js', isNot(isEmpty)),
+            d.matcherFile('subfile.dart.precompiled.js', isNot(isEmpty)),
+            d.matcherFile('subfile.dart.js.map', isNot(isEmpty)),
+            d.nothing('subfile.dart')
+          ])
+        ])
+      ])
+    ]).validate();
+  });
+}