[fsp] Implement storage::WatcherManager for FSP.

chrome/browser/chromeos/file_system_provider/watcher.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 CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_WATCHER_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_WATCHER_H_
 
 #include <map>
 #include <set>
 #include <string>
 
+#include "base/callback.h"
 #include "base/files/file_path.h"
+#include "storage/browser/fileapi/watcher_manager.h"
 #include "url/gurl.h"
 
 namespace chromeos {
 namespace file_system_provider {
 
 struct Watcher;
 struct Subscriber;
 
 // Key for storing a watcher in the map. There may be two watchers per path,
 // as long as one is recursive, and the other one not.
@@ skipping 19 matching lines @@
 // one subscriber per origin for the same watcher.
 struct Subscriber {
   Subscriber();
   ~Subscriber();
 
   // Origin of the subscriber.
   GURL origin;
 
   // Whether the subscriber should be restored after shutdown or not.
   bool persistent;
+
+  // Callback to be called for each watcher notification. It's optional, but
+  // not allowed for persistent watchers. In case of persistent subscribers,
+  // the notification should be handled using observers, as the callback can't
+  // be restored after shutdown.
+  storage::WatcherManager::NotificationCallback notification_callback;
 };
 
 // Represents a watcher on a file system.
 struct Watcher {
   Watcher();
   ~Watcher();
 
   // Map of subscribers for notifications of the watcher.
   Subscribers subscribers;
 
   // Path of the watcher.
   base::FilePath entry_path;
 
   // Whether watching is recursive or not.
   bool recursive;
 
   // Tag of the last notification for this watcher. May be empty if not
   // supported.
   std::string last_tag;
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_WATCHER_H_