Make UpgradeDetector work on the Mac

chrome/chrome_installer_util.gypi

 # Copyright (c) 2010 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.
 
 {
   'target_defaults': {
     'variables': {
       'installer_util_target': 0,
     },
     'target_conditions': [
@@ skipping 133 matching lines @@
             'installer/util/master_preferences_constants.h',
             'installer/util/version.cc',
             'installer/util/version.h',
           ],
           'include_dirs': [
             '<(DEPTH)',
           ],
         }
       ],
     }],
+    ['OS=="mac"', {
+      'targets': [
+        {
+          'target_name': 'installer_util',
+          'type': '<(library)',
+          'dependencies': [
+            '../base/base.gyp:base',
+          ],
+          'sources': [
+            'installer/util/version.cc',
+            'installer/util/version.h',
+          ],
+        }
+      ],
+    }],
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: