Use a mocked compositor for unit tests

chrome/chrome_tests.gypi

 # Copyright (c) 2011 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' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
@@ skipping 45 matching lines @@
         '../content/content.gyp:test_support_content',
         '../ipc/ipc.gyp:test_support_ipc',
         '../media/media.gyp:media_test_support',
         '../net/net.gyp:net',
         # 'test/base/test_url_request_context_getter.h' brings in this requirement.
         '../net/net.gyp:net_test_support',
         '../skia/skia.gyp:skia',
         '../testing/gmock.gyp:gmock',
         '../testing/gtest.gyp:gtest',
         '../third_party/leveldatabase/leveldatabase.gyp:leveldatabase',
+        '../ui/gfx/compositor/compositor.gyp:test_compositor',
       ],
       'export_dependent_settings': [
         'renderer',
         'app/policy/cloud_policy_codegen.gyp:policy',
         '../base/base.gyp:test_support_base',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
@@ skipping 4012 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }