Use new common utils where possible.

slave/skia_slave_scripts/flavor_utils/nacl_build_step_utils.py

 #!/usr/bin/env python
 # Copyright (c) 2013 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.
 
 """ Utilities for NaCl build steps. """
 
 from default_build_step_utils import DefaultBuildStepUtils
-from utils import shell_utils
+from py.utils import shell_utils
 
 import os
 
 
 ENV_VAR = 'NACL_SDK_ROOT'
 
 
 class NaclBuildStepUtils(DefaultBuildStepUtils):
   def Compile(self, target):
     os.environ[ENV_VAR] = self._step.args['nacl_sdk_root']
     cmd = [os.path.join('platform_tools', 'nacl', 'nacl_make'),
            target, 'BUILDTYPE=%s' % self._step.configuration,
            ]
     cmd.extend(self._step.default_make_flags)
     if os.name != 'nt':
       try:
         ccache = shell_utils.run(['which', 'ccache'], echo=False)
         if ccache:
           cmd.append('--use-ccache')
       except Exception:
         pass
     cmd.extend(self._step.make_flags)
     shell_utils.run(cmd)