Convert from using env['PLATFORM'] directly to using the more flexible...

chrome/plugin/plugin.scons

 # Copyright (c) 2006-2008 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.
 
 Import('env')
 
 env = env.Clone()
 
 env.SConscript([
     '$NPAPI_DIR/using_npapi.scons',
     '$SKIA_DIR/using_skia.scons',
 ], {'env':env})
 
 env.Prepend(
     CPPPATH = [
         '$CHROME_SRC_DIR',
     ],
 )
 
-if env['PLATFORM'] == 'win32':
+if env.Bit('windows'):
   env.Prepend(
       CPPPATH = [
           '$CHROME_DIR/tools/build/win',
       ],
   )
 
 input_files = [
     'chrome_plugin_host.cc',
     'npobject_proxy.cc',
     'npobject_stub.cc',
     'npobject_util.cc',
     'plugin_channel.cc',
     'plugin_channel_base.cc',
     'plugin_main.cc',
     'plugin_process.cc',
     'plugin_thread.cc',
     'webplugin_delegate_stub.cc',
     'webplugin_proxy.cc',
 ]
 
-if env['PLATFORM'] in ('posix', 'darwin'):
+if env.Bit('posix'):
   # TODO(port)
   to_be_ported_files = [
       'chrome_plugin_host.cc',
       'npobject_proxy.cc',
       'npobject_stub.cc',
       'npobject_util.cc',
       'plugin_channel.cc',
       'plugin_channel_base.cc',
       'plugin_main.cc',
       'plugin_process.cc',
       'plugin_thread.cc',
       'webplugin_delegate_stub.cc',
       'webplugin_proxy.cc',
   ]
   for remove in to_be_ported_files:
     input_files.remove(remove)
 
 env.ChromeStaticLibrary('plugin', input_files)