[FileSystem] Add another copy-or-move validation hook for post-write.

webkit/browser/fileapi/test_file_system_backend.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/browser/fileapi/test_file_system_backend.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 165 matching lines @@
   if (require_copy_or_move_validator_) {
     if (!copy_or_move_file_validator_factory_)
       *error_code = base::PLATFORM_FILE_ERROR_SECURITY;
     return copy_or_move_file_validator_factory_.get();
   }
   return NULL;
 }
 
 void TestFileSystemBackend::InitializeCopyOrMoveFileValidatorFactory(
     scoped_ptr<CopyOrMoveFileValidatorFactory> factory) {
+  // What purpose is this check serving?
   if (!require_copy_or_move_validator_) {
     DCHECK(!factory);
     return;
   }
   if (!copy_or_move_file_validator_factory_)
     copy_or_move_file_validator_factory_ = factory.Pass();
 }
 
 FileSystemOperation* TestFileSystemBackend::CreateFileSystemOperation(
     const FileSystemURL& url,
@@ skipping 38 matching lines @@
   return quota_util_->GetUpdateObservers(type);
 }
 
 void TestFileSystemBackend::AddFileChangeObserver(
     FileChangeObserver* observer) {
   quota_util_->AddFileChangeObserver(
       kFileSystemTypeTest, observer, quota_util_->task_runner());
 }
 
 }  // namespace fileapi