Add a mojom/StructTrait for display::Display.

ui/display/mojo/BUILD.gn

 # Copyright 2016 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.
 
-component("mojo") {
+import("//mojo/public/tools/bindings/mojom.gni")
+
+component("type_converter") {
   output_name = "mojo_display_lib"
 
   public_deps = [
     "//services/ui/public/interfaces",
     "//ui/display",
   ]
 
   defines = [ "MOJO_DISPLAY_IMPLEMENTATION" ]
 
   sources = [
     "display_type_converters.cc",
     "display_type_converters.h",
     "mojo_display_export.h",
   ]
 }
+
+mojom("mojo") {
+  sources = [
+    "display.mojom",
+  ]
+
+  public_deps = [
+    "//ui/gfx/geometry/mojo",
+  ]
+}
+
+mojom("test_interfaces") {
+  sources = [
+    "display_struct_traits_test.mojom",
+  ]
+
+  public_deps = [
+    ":mojo",
+  ]
+}