Make the gyp files more cross-platform across the Unices

chrome/common_constants.gypi

 # Copyright (c) 2009 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': {
       'common_constants_target': 0,
     },
     'target_conditions': [
@@ skipping 45 matching lines @@
     {
       'target_name': 'common_constants',
       'type': '<(library)',
       'variables': {
         'common_constants_target': 1,
       },
       'dependencies': [
         '../base/base.gyp:base',
       ],
       'conditions': [
-        ['OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
+        ['toolkit_uses_gtk==1', {
           'dependencies': ['../build/linux/system.gyp:gtk'],
         }],
       ],
     },
   ],
   'conditions': [
     ['OS=="win"', {
       'targets': [
         {
           'target_name': 'common_constants_win64',
@@ skipping 10 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }