[fsp] Add support for observing entries and notifying about changes.

chrome/browser/chromeos/file_system_provider/provided_file_system_observer.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_PROVIDED_FILE_SYSTEM_OBSERVER_H_
+#define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_OBSERVER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+
+namespace chromeos {
+namespace file_system_provider {
+
+class ProvidedFileSystemInfo;
+class RequestManager;
+
+// Observer class to be notified about changes happened to the provided file
+// system, especially observed entries.
+class ProvidedFileSystemObserver {
+ public:
+  struct ChildChange;
+
+  // Type of a change to an observed entry.
+  enum ChangeType { CHANGED, DELETED };
+
+  // Lust of child changes.
+  typedef std::vector<ChildChange> ChildChanges;
+
+  // Represents an observed entry on the file system.
+  struct ObservedEntry {
+    ObservedEntry();
+    ~ObservedEntry();
+
+    base::FilePath entry_path;
+    bool recursive;
+    std::string last_tag;
+  };
+
+  // Describes a change in an entry contained in an observed directory.
+  struct ChildChange {
+    ChildChange();
+    ~ChildChange();
+
+    base::FilePath entry_path;
+    ChangeType change_type;
+  };
+
+  // Called when an observed entry is changed, including removals. |callback|

[mtomasz, 2014/10/03 04:22:48]

As described before, the passed |callback| is created using
AutoUpdate::CreateCallback. When all of such callbacks are executed, then it
means that all observers finished handling this event, and the tag will be
updated.

+  // *must* be called after the entry change is handled. Once all observers
+  // call the callback, the tag will be updated and OnObservedEntryTagUpdated
+  // called.
+  virtual void OnObservedEntryChanged(
+      const ProvidedFileSystemInfo& file_system_info,
+      const base::FilePath& observed_path,
+      ChangeType change_type,
+      const ChildChanges& child_changes,
+      const base::Closure& callback) = 0;
+
+  // Called when tag value is updated for the observed entry.
+  virtual void OnObservedEntryTagUpdated(
+      const ProvidedFileSystemInfo& file_system_info,
+      const base::FilePath& observed_path) = 0;
+
+  // Called when list of observed entries is changed.
+  virtual void OnObservedEntryListChanged(
+      const ProvidedFileSystemInfo& file_system_info) = 0;
+};
+
+}  // namespace file_system_provider
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_OBSERVER_H_