ozone/platform/wayland: Add WaylandTest base class to eliminate redundancy

ui/ozone/platform/wayland/wayland.gypi

 # 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.
 
 {
   'variables': {
     'internal_ozone_platform_deps': [
       'ozone_platform_wayland',
     ],
     'internal_ozone_platform_unittest_deps': [
@@ skipping 52 matching lines @@
         '../../third_party/wayland/wayland.gyp:wayland_server',
         '../gfx/gfx.gyp:gfx_test_support',
       ],
       'direct_dependent_settings': {
         'sources': [
           'fake_server.cc',
           'fake_server.h',
           'mock_platform_window_delegate.cc',
           'wayland_display_unittest.cc',
           'wayland_surface_factory_unittest.cc',
+          'wayland_test.cc',
+          'wayland_test.h',
           'wayland_window_unittest.cc',
         ],
       },
     },
   ],
 }