ozone: Add missing dependencies to build

ui/ozone/platform/test/BUILD.gn

 # Copyright 2014 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.
 
 source_set("test") {
   sources = [
     "ozone_platform_test.cc",
     "ozone_platform_test.h",
     "test_window.cc",
     "test_window.h",
     "test_window_manager.cc",
     "test_window_manager.h",
   ]
 
   deps = [
     "//base",
     "//skia",
     "//ui/base",
     "//ui/gfx/geometry",
     "//ui/events/ozone:events_ozone_layout",
+    "//ui/events/platform",
   ]
 }