drive: Stop using /dev/null to store an empty file to the cache from CreateFileOperation

chrome/browser/chromeos/drive/file_system/create_file_operation.cc

 // Copyright 2013 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 "chrome/browser/chromeos/drive/file_system/create_file_operation.h"
 
 #include <string>
 
+#include "base/file_util.h"
 #include "chrome/browser/chromeos/drive/drive.pb.h"
 #include "chrome/browser/chromeos/drive/file_cache.h"
 #include "chrome/browser/chromeos/drive/file_system/operation_observer.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
 #include "chrome/browser/chromeos/drive/job_scheduler.h"
 #include "chrome/browser/chromeos/drive/resource_entry_conversion.h"
 #include "chrome/browser/chromeos/drive/resource_metadata.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/mime_util.h"
 
@@ skipping 68 matching lines @@
   // Depending on timing, the metadata may have inserted via change list feed
   // already. So, FILE_ERROR_EXISTS is not an error.
   if (error == FILE_ERROR_EXISTS)
     error = FILE_ERROR_OK;
 
   if (error == FILE_ERROR_OK) {
     // At this point, upload to the server is fully succeeded.
     // Populate the |file_path| which will be used to notify the observer.
     *file_path = metadata->GetFilePath(entry.resource_id());
 
-    // Also store the entry to the cache. Here, failure is not a fatal error,
-    // so ignore the returned code.
-    FileError cache_store_error = cache->Store(
-        entry.resource_id(),
-        entry.file_specific_info().file_md5(),
-        base::FilePath(util::kSymLinkToDevNull),
-        internal::FileCache::FILE_OPERATION_COPY);
-
+    // Also store an empty file to the cache.
+    // Here, failure is not a fatal error, so ignore the returned code.
+    FileError cache_store_error = FILE_ERROR_FAILED;
+    base::FilePath empty_file;
+    if (file_util::CreateTemporaryFile(&empty_file)) {
+      cache_store_error =  cache->Store(
+          entry.resource_id(),
+          entry.file_specific_info().file_md5(),
+          empty_file,
+          internal::FileCache::FILE_OPERATION_MOVE);
+    }
     DLOG_IF(WARNING, cache_store_error != FILE_ERROR_OK)
         << "Failed to store a cache file: "
         << FileErrorToString(cache_store_error)
         << ", resource_id: " << entry.resource_id();
   }
 
   return error;
 }
 
 }  // namespace
@@ skipping 101 matching lines @@
 
   // Notify observer if the file creation process is successfully done.
   if (error == FILE_ERROR_OK)
     observer_->OnDirectoryChangedByOperation(file_path->DirName());
 
   callback.Run(error);
 }
 
 }  // namespace file_system
 }  // namespace drive