Convert drive::FileWriteHelper to a single function for simplification.

chrome/browser/chromeos/drive/write_on_cache_file.cc

Index: chrome/browser/chromeos/drive/write_on_cache_file.cc
diff --git a/chrome/browser/chromeos/drive/write_on_cache_file.cc b/chrome/browser/chromeos/drive/write_on_cache_file.cc
new file mode 100644
index 0000000000000000000000000000000000000000..12d2e7be0d26b4621b4405d964145b112286bf1a
--- /dev/null
+++ b/chrome/browser/chromeos/drive/write_on_cache_file.cc
@@ -0,0 +1,58 @@
+// 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 "chrome/browser/chromeos/drive/write_on_cache_file.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "chrome/browser/chromeos/drive/file_system_interface.h"
+#include "content/public/browser/browser_thread.h"
+
+using content::BrowserThread;
+
+namespace drive {
+
+namespace {
+
+// Runs |file_io_task_callback| in blocking pool and runs |close_callback|
+// in the UI thread after that.
+void WriteOnCacheFileAfterOpenFile(
+    const base::FilePath& drive_path,
+    const WriteOnCacheFileCallback& file_io_task_callback,
+    FileError error,
+    const base::FilePath& local_cache_path,
+    const base::Closure& close_callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  if (error == FILE_ERROR_OK) {
+    DCHECK(!close_callback.is_null());
+    BrowserThread::GetBlockingPool()->PostTaskAndReply(
+        FROM_HERE,
+        base::Bind(file_io_task_callback, error, local_cache_path),
+        close_callback);
+  } else {
+    BrowserThread::GetBlockingPool()->PostTask(
+        FROM_HERE,
+        base::Bind(file_io_task_callback, error, local_cache_path));
+
+  }
+}
+
+}  // namespace
+
+void WriteOnCacheFile(FileSystemInterface* file_system,
+                      const base::FilePath& path,
+                      const WriteOnCacheFileCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(file_system);
+  DCHECK(!callback.is_null());
+
+  file_system->OpenFile(
+      path,
+      OPEN_OR_CREATE_FILE,
+      base::Bind(&WriteOnCacheFileAfterOpenFile, path, callback));
+}
+
+}  // namespace drive