Rename "test" ozone platform to "headless"

ui/ozone/platform/test/test.gypi

-# 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.
-
-{
-  'variables': {
-    'internal_ozone_platform_deps': [
-      'ozone_platform_test',
-    ],
-    'internal_ozone_platforms': [
-      'test'
-    ],
-  },
-  'targets': [
-    {
-      'target_name': 'ozone_platform_test',
-      'type': 'static_library',
-      'defines': [
-        'OZONE_IMPLEMENTATION',
-      ],
-      'dependencies': [
-        '../../base/base.gyp:base',
-        '../base/ui_base.gyp:ui_base',
-        '../events/events.gyp:events',
-        '../events/ozone/events_ozone.gyp:events_ozone_layout',
-        '../events/platform/events_platform.gyp:events_platform',
-        '../gfx/gfx.gyp:gfx',
-      ],
-      'sources': [
-        'client_native_pixmap_factory_test.cc',
-        'client_native_pixmap_factory_test.h',
-        'ozone_platform_test.cc',
-        'ozone_platform_test.h',
-        'test_surface_factory.cc',
-        'test_surface_factory.h',
-        'test_window.cc',
-        'test_window.h',
-        'test_window_manager.cc',
-        'test_window_manager.h',
-      ],
-    },
-  ],
-}