[Android] DeviceUtils change to make Install work without md5 binary.

build/android/pylib/utils/md5sum_test.py

 #!/usr/bin/env python
 # Copyright 2014 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 os
 import sys
 import unittest
 
 from pylib import cmd_helper
 from pylib import constants
 from pylib.utils import md5sum
 
 sys.path.append(
     os.path.join(constants.DIR_SOURCE_ROOT, 'third_party', 'pymock'))
 import mock
 
 TEST_OUT_DIR = os.path.join('test', 'out', 'directory')
 HOST_MD5_EXECUTABLE = os.path.join(TEST_OUT_DIR, 'md5sum_bin_host')
 
 class Md5SumTest(unittest.TestCase):
 
   def setUp(self):
     self._patchers = [
         mock.patch('pylib.constants.GetOutDirectory',
                    new=mock.Mock(return_value=TEST_OUT_DIR)),
+        mock.patch('os.path.exists',
+                   new=mock.Mock(return_value=True)),
     ]
     for p in self._patchers:
       p.start()
 
   def tearDown(self):
     for p in self._patchers:
       p.stop()
 
   def testCalculateHostMd5Sums_singlePath(self):
     test_path = '/test/host/file.dat'
@@ skipping 137 matching lines @@
       self.assertEquals('/storage/emulated/legacy/test/file1.dat', out[1].path)
       device.adb.Push.assert_called_once_with(
           '/tmp/test/script/file.sh', '/data/local/tmp/test/script/file.sh')
       device.RunShellCommand.assert_called_once_with(
           ['sh', '/data/local/tmp/test/script/file.sh'])
 
 
 if __name__ == '__main__':
   unittest.main(verbosity=2)