Call WatcherManager functions on the IO thread.

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/callback_forward.h"
 #include "base/files/file.h"
 
 namespace storage {
 
 class FileSystemURL;
 
 // An interface for providing entry observing capability for file system
 // backends.
 //
+// All member functions must be called on the IO thread. Callbacks will be
+// called on the IO thread.
+//
 // 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 ChangeType { CHANGED, DELETED };
 
   typedef base::Callback<void(base::File::Error result)> StatusCallback;
   typedef base::Callback<void(ChangeType change_type)> NotificationCallback;
 
   virtual ~WatcherManager() {}
@@ skipping 17 matching lines @@
 
   // 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_