ozone: Add ozone_unittests target

ui/gfx/ozone/gfx_ozone.gyp

 # 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': {
     'chromium_code': 1,
   },
   'targets': [{
     'target_name': 'gfx_ozone',
     'type': '<(component)',
     'defines': [
       'GFX_IMPLEMENTATION',
     ],
     'dependencies': [
       '../../../base/base.gyp:base',
       '../../../skia/skia.gyp:skia',
+      '../gfx.gyp:gfx',
       '../gfx.gyp:gfx_geometry',
     ],
     'sources': [
       'impl/file_surface_factory.cc',
       'impl/file_surface_factory.h',
       'surface_factory_ozone.cc',
       'surface_factory_ozone.h',
       'surface_ozone_egl.h',
       'surface_ozone_canvas.h',
       'overlay_candidates_ozone.cc',
       'overlay_candidates_ozone.h',
     ],
   }],
 }