Add a mojom/StructTrait for display::Display.

ui/display/mojo/BUILD.gn

Index: ui/display/mojo/BUILD.gn
diff --git a/ui/display/mojo/BUILD.gn b/ui/display/mojo/BUILD.gn
index 6ef3b4b31b406d85dac60ff245067571d487ccaf..f810aece6f11044b1f98a01da9f0a778fdc51bd8 100644
--- a/ui/display/mojo/BUILD.gn
+++ b/ui/display/mojo/BUILD.gn
@@ -2,7 +2,9 @@
 # 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 = [
@@ -18,3 +20,23 @@ component("mojo") {
     "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",
+  ]
+}