Allow overriding GYP_GENERATORS in chromium.gyp_env.

build/gyp_chromium

 #!/usr/bin/env python
 
 # 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.
 
 # This script is wrapper for Chromium that adds some support for how GYP
 # is invoked by Chromium beyond what can be done in the gclient hooks.
 
 import glob
@@ skipping 41 matching lines @@
   file_contents = open(file_path).read()
   try:
     file_data = eval(file_contents, {'__builtins__': None}, None)
   except SyntaxError, e:
     e.filename = os.path.abspath(file_path)
     raise
   supported_vars = ( 'CHROMIUM_GYP_FILE',
                      'CHROMIUM_GYP_SYNTAX_CHECK',
                      'GYP_DEFINES',
                      'GYP_GENERATOR_FLAGS',
-                     'GYP_GENERATOR_OUTPUT', )
+                     'GYP_GENERATOR_OUTPUT',
+                     'GYP_GENERATORS', )
   for var in supported_vars:
     val = file_data.get(var)
     if val:
       if var in os.environ:
         print 'INFO: Environment value for "%s" overrides value in %s.' % (
             var, os.path.abspath(file_path)
         )
       else:
         os.environ[var] = val
 
@@ skipping 89 matching lines @@
   # to enfore syntax checking.
   syntax_check = os.environ.get('CHROMIUM_GYP_SYNTAX_CHECK')
   if syntax_check and int(syntax_check):
     args.append('--check')
 
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Off we go...
   sys.exit(gyp.main(args))