Quota calculation is wrong in cross-filesystem operation

webkit/fileapi/file_system_usage_cache.cc

 // 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.
 
 #include "webkit/fileapi/file_system_usage_cache.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/pickle.h"
 
 namespace fileapi {
 
 const FilePath::CharType FileSystemUsageCache::kUsageFileName[] =
     FILE_PATH_LITERAL(".usage");
-const char FileSystemUsageCache::kUsageFileHeader[] = "FSU4";
+const char FileSystemUsageCache::kUsageFileHeader[] = "FSU5";
 const int FileSystemUsageCache::kUsageFileHeaderSize = 4;
 
 /* Pickle::{Read,Write}Bool treat bool as int */
 const int FileSystemUsageCache::kUsageFileSize =
     sizeof(Pickle::Header) +
     FileSystemUsageCache::kUsageFileHeaderSize +
     sizeof(int) + sizeof(int32) + sizeof(int64);
 
 // static
 int64 FileSystemUsageCache::GetUsage(const FilePath& usage_file_path) {
@@ skipping 151 matching lines @@
   if (bytes_written != kUsageFileSize)
     return -1;
 
   if (file_util::ReplaceFile(temporary_usage_file_path, usage_file_path))
     return bytes_written;
   else
     return -1;
 }
 
 }  // namespace fileapi