replace platform conditions with os_posix and os_bsd where applicable

ppapi/ppapi_tests.gypi

 # 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.
 
 {
   'targets': [
      {
       'target_name': 'ppapi_example',
       'dependencies': [
         'ppapi.gyp:ppapi_cpp'
@@ skipping 224 matching lines @@
         'shared_impl/test_globals.h',
       ],
     },
     {
       'target_name': 'ppapi_example_skeleton',
       'suppress_wildcard': 1,
       'type': 'none',
       'direct_dependent_settings': {
         'product_name': '>(_target_name)',
         'conditions': [
-          ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris" or OS=="android"', {
+          ['os_posix==1 and OS!="mac"', {
             'cflags': ['-fvisibility=hidden'],
             'type': 'shared_library',
             # -gstabs, used in the official builds, causes an ICE. Simply remove
             # it.
             'cflags!': ['-gstabs'],
           }],
           ['OS=="win"', {
             'type': 'shared_library',
           }],
           ['OS=="mac"', {
@@ skipping 250 matching lines @@
               # Var_deprecated fails in TestPassReference, and we probably won't
               # fix it.
               #'tests/test_var_deprecated.cc'
             ],
           },
         },
       ],
     }],
   ],
 }