Create an apptesting framework for dart.

third_party/dart-packages/path/BUILD.gn

+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//mojo/public/dart/rules.gni")
+
+dart_package("path") {
+  sources = [
+    "path/path.dart",
+    "path/src/characters.dart",
+    "path/src/context.dart",
+    "path/src/internal_style.dart",
+    "path/src/parsed_path.dart",
+    "path/src/path_exception.dart",
+    "path/src/style.dart",
+    "path/src/utils.dart",
+    "path/src/style/posix.dart",
+    "path/src/style/url.dart",
+    "path/src/style/windows.dart",
+  ]
+}