Support for ARM NaCl untrusted runtime build.

build/download_nacl_toolchains.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Shim to run nacl toolchain download script only if there is a nacl dir."""
 
 import os
 import sys
 
@@ skipping 16 matching lines @@
   import download_toolchains
 
   # TODO (robertm): Finish getting PNaCl ready for prime time.
   # BUG:
   # We remove this --optional-pnacl argument, and instead replace it with
   # --no-pnacl for most cases.  However, if the bot name is the pnacl_sdk
   # bot then we will go ahead and download it.  This prevents increasing the
   # gclient sync time for developers, or standard Chrome bots.
   if '--optional-pnacl' in args:
     args.remove('--optional-pnacl')
+    # By default we don't use PNaCl toolchain yet, unless on ARM, where
+    # there is no other toolchain to build untrusted code at the moment.
+    # So analyze if we're building for ARM, or on SDK buildbot.
+    # TODO(olonho): we need to invent more reliable way to get build
+    # configuration info, to know if we're building for ARM.
+    use_pnacl = False
+    if 'target_arch=arm' in os.environ.get('GYP_DEFINES', ''):
+      use_pnacl = True
     buildbot_name = os.environ.get('BUILDBOT_BUILDERNAME', '')
     if buildbot_name.find('pnacl') >= 0 and  buildbot_name.find('sdk') >= 0:
+      use_pnacl = True
+    if use_pnacl:
       print '\n*** DOWNLOADING PNACL TOOLCHAIN ***\n'
     else:
       args.append('--no-pnacl')
 
   download_toolchains.Main(args)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv[1:]))
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