Media Galleries API Picasa: Add file watch to invalidate database data on disk write.

chrome/browser/media_galleries/fileapi/file_path_watcher_util.h

+// 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.
+
+#ifndef CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_FILE_PATH_WATCHER_UTIL_H_
+#define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_FILE_PATH_WATCHER_UTIL_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/files/file_path.h"
+#include "base/files/file_path_watcher.h"
+
+namespace chrome {
+
+typedef base::Callback<void(scoped_ptr<base::FilePathWatcher> watcher)>
+    FileWatchStartedCallback;
+
+// Called on the MediaTaskRunner to begin a file watch.
+// |watch_started_callback| is responsible for taking ownership of the
+// file watcher upon start. All callbacks are run on the MediaTaskRunner.
+void StartFilePathWatchOnMediaTaskRunner(
+    const base::FilePath& path,
+    const FileWatchStartedCallback& watch_started_callback,
+    const base::FilePathWatcher::Callback& path_changed_callback);
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_FILE_PATH_WATCHER_UTIL_H_