[ew] Simplify the entry watcher logic.

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 };
+
   typedef base::Callback<void(base::File::Error result)> StatusCallback;
-
-  // Observes watched entries.
-  class Observer {
-   public:
-    Observer() {}
-    virtual ~Observer() {}
-
-    // Notifies about an entry represented by |url| being changed.
-    virtual void OnEntryChanged(const FileSystemURL& url) = 0;
-
-    // Notifies about an entry represented by |url| being removed.
-    virtual void OnEntryRemoved(const FileSystemURL& url) = 0;
-  };
+  typedef base::Callback<void(Action action)> NotificationCallback;
 
   virtual ~WatcherManager() {}
 
-  virtual void AddObserver(Observer* observer) = 0;
-  virtual void RemoveObserver(Observer* observer) = 0;
-  virtual bool HasObserver(Observer* observer) const = 0;
-
   // Observes a directory entry. 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.
-  virtual void WatchDirectory(const FileSystemURL& url,
-                              bool recursive,
-                              const StatusCallback& callback) = 0;
+  // called with the FILE_OK error code. |notification_callback| is called for
+  // every change related to the watched directory.
+  virtual void WatchDirectory(

[benwells, 2014/10/23 02:10:34]

Is this implemented / called by anything?

[mtomasz, 2014/10/23 02:15:11]

Not now, but I'll need it for upcoming CLs. FSP code is going to implement this
interface. chrome.fileManagerPrivate will use fsp's implementation of it to set
watchers.

In the future watcher logic in chrome.fileManagerPrivate will be replaced with
Entry Watcher API.

+      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;
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_FILEAPI_WATCHER_MANAGER_H_