Make unit_tests compile in Mac GN

chrome/chrome_tests_unit.gypi

 # Copyright 2012 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': {
     'chrome_unit_tests_sources': [
       # histograms.xml is analyzed by AboutFlagsHistogramTest, so this
       # dependency is needed to make commit bots run unit_tests on
       # histograms.xml changes.
       '../tools/metrics/histograms/histograms.xml',
@@ skipping 1625 matching lines @@
     # Sources for Offline pages. For now only for Android.
     'chrome_unit_tests_offline_pages_sources': [
       'browser/android/offline_pages/offline_page_mhtml_archiver_unittest.cc',
     ],
   },
   'targets': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       #
-      # GN version: //chrome/test:test_support
+      # GN version: //chrome/test:test_support but that is split apart into
+      # separate test_support targets for that various subdirectories under
+      # chrome.
       'target_name': 'test_support_common',
       'type': 'static_library',
       'dependencies': [
         # NOTE: New dependencies should generally be added in the OS!="ios"
         # dependencies block below, rather than here.
         'browser',
         'chrome_resources.gyp:chrome_resources',
         'chrome_resources.gyp:chrome_strings',
         'chrome_resources.gyp:theme_resources',
         'common',
@@ skipping 1319 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }