Support serving from multiple directories using "pub serve".

sdk/lib/_internal/pub/test/serve/roots/serves_web_and_test_dirs_by_default_test.dart

Index: sdk/lib/_internal/pub/test/serve/roots/serves_web_and_test_dirs_by_default_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/roots/serves_web_and_test_dirs_by_default_test.dart b/sdk/lib/_internal/pub/test/serve/roots/serves_web_and_test_dirs_by_default_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c53e8ba621bd47e8736aff49b0b91119ad063a36
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/serve/roots/serves_web_and_test_dirs_by_default_test.dart
@@ -0,0 +1,27 @@
+// Copyright (c) 2014, 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.
+
+library pub_tests;
+
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+import '../utils.dart';
+
+main() {
+  initConfig();
+  integration("serves web/ and test/ dirs by default", () {
+    d.dir(appPath, [
+      d.appPubspec(),
+      d.dir("web", [d.file("foo", "contents")]),
+      d.dir("test", [d.file("bar", "contents")]),
+      d.dir("example", [d.file("baz", "contents")])
+    ]).create();
+
+    pubServe();
+    requestShouldSucceed("foo", "contents", root: "web");
+    requestShouldSucceed("bar", "contents", root: "test");
+    requestShould404("baz", root: "web");
+    endPubServe();
+  });
+}