Add mojom::DisplayController.

services/ui/public/interfaces/display/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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("display") {
   sources = [
     "display.mojom",
+    "display_controller.mojom",
   ]
 
   public_deps = [
     "//ui/gfx/geometry/mojo",
   ]
 
   use_new_wrapper_types = false
 }
 
 mojom("test_interfaces") {
   sources = [
     "display_struct_traits_test.mojom",
   ]
 
   public_deps = [
     ":display",
   ]
 
   use_new_wrapper_types = false
 }