Add a function to parse metadata into a usable object.

lib/src/backend/metadata.dart

Index: lib/src/backend/metadata.dart
diff --git a/lib/src/backend/metadata.dart b/lib/src/backend/metadata.dart
new file mode 100644
index 0000000000000000000000000000000000000000..738a7cf5e692457fee3d5a72ff9c5c28aedeaf97
--- /dev/null
+++ b/lib/src/backend/metadata.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2015, 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 unittest.backend.metadata;
+
+/// Metadata for a test or test suite.
+///
+/// This metadata comes from declarations on the test itself; it doesn't include
+/// configuration from the user.
+class Metadata {
+  /// The expressions indicating which platforms the suite supports.
+  final String testOn;

[Bob Nystrom, 2015/03/12 21:03:21]

Why is this a String and not a TestOn?

[nweiz, 2015/03/12 23:40:22]

It should really be a PlatformSelector, actually, but that class doesn't exist
yet so I'm just using a String as a placeholder.

+
+  Metadata(this.testOn);
+}