compositor: Fix compositor_unittests build on Linux.

ui/gfx/compositor/compositor.gyp

 # 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': {
     'chromium_code': 1,
   },
   'target_defaults': {
     'sources/': [
@@ skipping 78 matching lines @@
         '<(DEPTH)/testing/gtest.gyp:gtest',
         '<(DEPTH)/ui/gfx/gl/gl.gyp:gl',
         '<(DEPTH)/ui/ui.gyp:gfx_resources',
         '<(DEPTH)/ui/ui.gyp:ui',
         '<(DEPTH)/ui/ui.gyp:ui_resources',
         'compositor',
       ],
       'sources': [
         'layer_unittest.cc',
         'run_all_unittests.cc',
+        'test_compositor_host.cc',
         'test_compositor_host.h',
         'test_compositor_host_win.cc',
         'test_suite.cc',
         'test_suite.h',
         '<(SHARED_INTERMEDIATE_DIR)/ui/gfx/gfx_resources.rc',
         '<(SHARED_INTERMEDIATE_DIR)/ui/ui_resources/ui_resources.rc',
       ],
     },
   ],
 }