Add a mojom/StructTrait for display::Display.

ui/display/BUILD.gn

Index: ui/display/BUILD.gn
diff --git a/ui/display/BUILD.gn b/ui/display/BUILD.gn
index 55d1e56fc4a4be19eeeb05f29cf46c4ead8818eb..9ab71e22006a31b0287bce7c2a2822c63a4dd11c 100644
--- a/ui/display/BUILD.gn
+++ b/ui/display/BUILD.gn
@@ -195,8 +195,8 @@ test("display_unittests") {
     ":display",
     ":test_support",
     "//base",
-    "//base/test:run_all_unittests",
     "//base/test:test_support",
+    "//mojo/edk/test:run_all_unittests",
     "//testing/gtest",
     "//ui/display/types",
     "//ui/display/util",
@@ -204,6 +204,12 @@ test("display_unittests") {
     "//ui/gfx/geometry",
   ]
 
+  if (!is_ios) {
+    sources += [ "mojo/display_struct_traits_unittest.cc" ]
+
+    deps += [ "//ui/display/mojo:test_interfaces" ]
+  }
+
   if (is_chromeos) {
     deps += [ ":test_util" ]
   }