When updating md5sum_bin, wipe the directory first

build/android/pylib/utils/md5sum.py

 # 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 collections
 import logging
 import os
 import posixpath
 import re
 import tempfile
@@ skipping 77 matching lines @@
   md5sum_script += ';'.join('$a %s' % p for p in paths)
   # Don't fail the script if the last md5sum fails (due to file not found)
   # Note: ":" is equivalent to "true".
   md5sum_script += ';:'
   try:
     out = device.RunShellCommand(md5sum_script, check_return=True)
   except device_errors.AdbShellCommandFailedError as e:
     # Push the binary only if it is found to not exist
     # (faster than checking up-front).
     if e.status == 2:
+      # If files were previously pushed as root (adbd running as root), trying
+      # to re-push as non-root causes the push command to report success, but
+      # actually fail. So, wipe the directory first.
+      device.RunShellCommand(['rm', '-rf', MD5SUM_DEVICE_LIB_PATH],
+                             as_root=True, check_return=True)
       device.adb.Push(md5sum_dist_path, MD5SUM_DEVICE_LIB_PATH)
       out = device.RunShellCommand(md5sum_script, check_return=True)
     else:
       raise
 
   return _ParseMd5SumOutput(out)
 
 
 def _ParseMd5SumOutput(out):
   hash_and_path = (l.split(None, 1) for l in out
                    if l and _STARTS_WITH_CHECKSUM_RE.match(l))
   return dict((p, h) for h, p in hash_and_path)