Media Gallery: Implement a basic version of GetMediaFileSystems().

chrome/browser/media_gallery/media_file_system_registry.h

+// 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.
+
+// MediaFileSystemRegistry registers pictures directories as File API
+// filesystems and keeps track of the path to filesystem ID mappings.
+// In the near future, MediaFileSystemRegistry will also support media devices.
+
+#ifndef CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_
+#define CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_
+#pragma once
+
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/lazy_instance.h"
+
+class FilePath;
+
+namespace fileapi {
+class IsolatedContext;
+}
+
+namespace chrome {
+
+class MediaFileSystemRegistry {
+ public:
+  // (Filesystem ID, path)
+  typedef std::pair<std::string, FilePath> MediaFSIDAndPath;
+
+  // The instance is lazily created per browser process.
+  static MediaFileSystemRegistry* GetInstance();
+
+  // Returns the list of media filesystem IDs and paths.
+  // Called on the UI thread.
+  std::vector<MediaFSIDAndPath> GetMediaFileSystems() const;
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<MediaFileSystemRegistry>;
+
+  // Mapping of media directories to filesystem IDs.
+  typedef std::map<FilePath, std::string> MediaPathToFSIDMap;
+
+  // Obtain an instance of this class via GetInstance().
+  MediaFileSystemRegistry();
+  virtual ~MediaFileSystemRegistry();
+
+  // Registers a path as a media file system.
+  void RegisterPathAsFileSystem(const FilePath& path);
+
+  MediaPathToFSIDMap media_fs_map_;

[kinuko, 2012/05/24 05:17:05]

Do we want to have a lock to guard it or may we want to make the Registry class
NonThreadSafe?

[Lei Zhang, 2012/05/24 22:55:41]

For now, I think we only need to access |media_fs_map_| on the UI thread. I've
added additional comments and DCHECKs.

+
+  DISALLOW_COPY_AND_ASSIGN(MediaFileSystemRegistry);
+};
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_