AU: FilesystemCopierAction: copy bit-exactly

src/platform/update_engine/utils.cc

 // Copyright (c) 2009 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.
 
 #include "update_engine/utils.h"
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <dirent.h>
 #include <errno.h>
@@ skipping 315 matching lines @@
     return false;
   }
   return true;
 }
 
 bool UnmountFilesystem(const string& mountpoint) {
   TEST_AND_RETURN_FALSE_ERRNO(umount(mountpoint.c_str()) == 0);
   return true;
 }
 
+const char* GetGErrorMessage(const GError* error) {
+  if (!error)
+    return "Unknown error.";
+  return error->message;
+}
+
 const char* const kStatefulPartition = "/mnt/stateful_partition";
 
 }  // namespace utils
 
 }  // namespace chromeos_update_engine