[aura-mus] Add ui::CursorData, with mojo serialization.

services/ui/public/interfaces/cursor/cursor_struct_traits_test.mojom

Index: services/ui/public/interfaces/cursor/cursor_struct_traits_test.mojom
diff --git a/services/ui/public/interfaces/cursor/cursor_struct_traits_test.mojom b/services/ui/public/interfaces/cursor/cursor_struct_traits_test.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..569b3df919f750ea6aec825bcec241b7a390944a
--- /dev/null
+++ b/services/ui/public/interfaces/cursor/cursor_struct_traits_test.mojom
@@ -0,0 +1,12 @@
+// Copyright 2017 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.
+
+module ui.mojom;
+
+import "services/ui/public/interfaces/cursor/cursor.mojom";
+
+interface CursorStructTraitsTest {
+  [Sync]
+  EchoCursorData(CursorData in) => (CursorData out);
+};