Create mojom and StructTraits for ui/display/types/display_mode.cc

ui/display/mojo/display_struct_traits_test.mojom

Index: ui/display/mojo/display_struct_traits_test.mojom
diff --git a/ui/display/mojo/display_struct_traits_test.mojom b/ui/display/mojo/display_struct_traits_test.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..a56a864d1bfb38601565fe923bced96392fef8c3
--- /dev/null
+++ b/ui/display/mojo/display_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 display.mojom;
+
+import "ui/display/mojo/display_mode_mojo.mojom";
+
+interface DisplayStructTraitsTest {
+  [Sync]
+  EchoDisplayModeMojo(DisplayModeMojo in) => (DisplayModeMojo out);
+};