Adding native_client/build to the gyp module include path.

build/gyp_chromium

 #!/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.
 
 # 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
 import os
 import shlex
 import subprocess
 import sys
 
 script_dir = os.path.dirname(__file__)
 chrome_src = os.path.abspath(os.path.join(script_dir, os.pardir))
 
 sys.path.insert(0, os.path.join(chrome_src, 'tools', 'gyp', 'pylib'))
 import gyp
 
 # Add paths so that pymod_do_main(...) can import files.
 sys.path.insert(1, os.path.join(chrome_src, 'tools', 'grit'))
 sys.path.insert(1, os.path.join(chrome_src, 'chrome', 'tools', 'build'))
+sys.path.insert(1, os.path.join(chrome_src, 'native_client', 'build'))
 
 
 # On Windows, Psyco shortens warm runs of build/gyp_chromium by about
 # 20 seconds on a z600 machine with 12 GB of RAM, from 90 down to 70
 # seconds.  Conversely, memory usage of build/gyp_chromium with Psyco
 # maxes out at about 158 MB vs. 132 MB without it.
 #
 # Psyco uses native libraries, so we need to load a different
 # installation depending on which OS we are running under. It has not
 # been tested whether using Psyco on our Mac and Linux builds is worth
@@ skipping 128 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))