Add a mojom/StructTrait for display::Display.

services/ui/public/interfaces/BUILD.gn

Index: services/ui/public/interfaces/BUILD.gn
diff --git a/services/ui/public/interfaces/BUILD.gn b/services/ui/public/interfaces/BUILD.gn
index 66bce5553027e028824705c36504eb0cb4f85f3c..d49cdba8b55ff5145717b36bb60f4f25c47e6836 100644
--- a/services/ui/public/interfaces/BUILD.gn
+++ b/services/ui/public/interfaces/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
+import("//testing/test.gni")
 
 mojom("interfaces") {
   sources = [
@@ -45,3 +46,19 @@ mojom("interfaces") {
     "//ui/platform_window/mojo:interfaces",
   ]
 }
+
+test("ui_struct_traits_unittests") {
+  sources = [
+    "display/display_struct_traits_unittest.cc",
+  ]
+
+  deps = [
+    "//base",
+    "//base/test:test_support",
+    "//mojo/edk/test:run_all_unittests",
+    "//services/ui/public/interfaces/display:test_interfaces",
+    "//testing/gtest",
+    "//ui/display/types",
+    "//ui/gfx:test_support",
+  ]
+}