Attempt 3 at:

ui/aura/aura.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,
   },
   'targets': [
     {
@@ skipping 42 matching lines @@
         'window_observer.h',
         'window_types.h',
       ],
     },
     {
       'target_name': 'test_support_aura',
       'type': 'static_library',
       'dependencies': [
         '../../skia/skia.gyp:skia',
         '../../testing/gtest.gyp:gtest',
-        '../gfx/compositor/compositor.gyp:test_compositor',
         '../ui.gyp:ui',
         'aura',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'test/aura_test_base.cc',
         'test/aura_test_base.h',
         'test/event_generator.cc',
         'test/event_generator.h',
         'test/test_event_filter.cc',
         'test/test_event_filter.h',
         'test/test_stacking_client.cc',
         'test/test_stacking_client.h',
         'test/test_windows.cc',
         'test/test_windows.h',
         'test/test_window_delegate.cc',
         'test/test_window_delegate.h',
       ],
+      'conditions': [
+        ['use_webkit_compositor==0', {
+          'dependencies': [
+            '../gfx/compositor/compositor.gyp:test_compositor',
+          ],
+        }],
+      ],
     },
     {
       'target_name': 'aura_demo',
       'type': 'executable',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:base_i18n',
         '../../skia/skia.gyp:skia',
         '../../third_party/icu/icu.gyp:icui18n',
         '../../third_party/icu/icu.gyp:icuuc',
@@ skipping 15 matching lines @@
     },
     {
       'target_name': 'aura_unittests',
       'type': 'executable',
       'dependencies': [
         '../../base/base.gyp:test_support_base',
         '../../chrome/chrome_resources.gyp:packed_resources',
         '../../skia/skia.gyp:skia',
         '../../testing/gtest.gyp:gtest',
         '../gfx/compositor/compositor.gyp:compositor_test_support',
-        '../gfx/compositor/compositor.gyp:test_compositor',
         '../gfx/gl/gl.gyp:gl',
         '../ui.gyp:gfx_resources',
         '../ui.gyp:ui',
         '../ui.gyp:ui_resources',
         'test_support_aura',
         'aura',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'test/run_all_unittests.cc',
         'test/test_suite.cc',
         'test/test_suite.h',
         'root_window_unittest.cc',
         'event_filter_unittest.cc',
         'window_unittest.cc',
         '<(SHARED_INTERMEDIATE_DIR)/ui/gfx/gfx_resources.rc',
         '<(SHARED_INTERMEDIATE_DIR)/ui/ui_resources/ui_resources.rc',
       ],
       # osmesa GL implementation is used on linux.
       'conditions': [
         ['OS=="linux"', {
           'dependencies': [
             '<(DEPTH)/third_party/mesa/mesa.gyp:osmesa',
           ],
         }],
+        ['use_webkit_compositor==1', {
+          'dependencies': [
+            '../gfx/compositor/compositor.gyp:compositor',
+          ],
+        }, { # use_webkit_compositor!=1
+          'dependencies': [
+            '../gfx/compositor/compositor.gyp:test_compositor',
+          ],
+        }],
       ],
     },
   ],
 }