replace platform conditions with os_posix and os_bsd where applicable

printing/printing.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 243 matching lines @@
                     '$(SDKROOT)/usr/lib/libcups.dylib',
                   ]
                 },
               }, {
                 'link_settings': {
                   'libraries': [
                     '<!@(python cups_config_helper.py --libs)',
                   ],
                 },
               }],
-              [ 'OS == "openbsd"', {
+              [ 'os_bsd==1', {
                 'cflags': [
                   '<!@(python cups_config_helper.py --cflags)',
                 ],
               }],
             ],
           },
         }],
       ],
     },
   ],
 }