[fsp] Implement storage::WatcherManager for FSP.

storage/browser/fileapi/watcher_manager.h

 // Copyright 2014 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 STORAGE_BROWSER_FILEAPI_WATCHER_MANAGER_H_
 #define STORAGE_BROWSER_FILEAPI_WATCHER_MANAGER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/files/file.h"
 
-namespace base {
-class Time;
-}
-
 namespace storage {
 
 class FileSystemOperationContext;
 class FileSystemURL;
 
 // An interface for providing entry observing capability for file system
 // backends.
 //
 // It is NOT valid to give null callback to this class, and implementors
 // can assume that they don't get any null callbacks.
 class WatcherManager {
  public:
-  enum Action { CHANGED, REMOVED };
+  enum ChangeType { CHANGED, DELETED };
 
   typedef base::Callback<void(base::File::Error result)> StatusCallback;
-  typedef base::Callback<void(Action action)> NotificationCallback;
+  typedef base::Callback<void(ChangeType change_type)> NotificationCallback;
 
   virtual ~WatcherManager() {}
 
-  // Observes a directory entry. If the |recursive| mode is not supported then
+  // Adds an entry watcher. If the |recursive| mode is not supported then
   // FILE_ERROR_INVALID_OPERATION must be returned as an error. If the |url| is
-  // already watched, or setting up the watcher fails, then |callback|
-  // must be called with a specific error code. Otherwise |callback| must be
-  // called with the FILE_OK error code. |notification_callback| is called for
-  // every change related to the watched directory.
-  virtual void WatchDirectory(
+  // already watched with the same |recursive|, or setting up the watcher fails,
+  // then |callback| must be called with a specific error code.
+  //
+  // There may be up to two watchers for the same |url| as well as one of them
+  // is recursive, and the other one is not.
+  //
+  // In case of a success |callback| must be called with the FILE_OK error code.
+  // |notification_callback| is called for every change related to the watched
+  // directory.
+  virtual void AddWatcher(
       const FileSystemURL& url,
       bool recursive,
       const StatusCallback& callback,
       const NotificationCallback& notification_callback) = 0;
 
-  // Stops observing an entry represented by |url|.
-  virtual void UnwatchEntry(const FileSystemURL& url,
-                            const StatusCallback& callback) = 0;
+  // Removes a watcher represented by |url| in |recursive| mode.
+  virtual void RemoveWatcher(const FileSystemURL& url,
+                             bool recursive,
+                             const StatusCallback& callback) = 0;
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_FILEAPI_WATCHER_MANAGER_H_