[fsp] Introduce file_system_provider::Service class for the FileSystemProvider API.

chrome/browser/chromeos/file_system_provider/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_OBSERVER_H_
+#define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_OBSERVER_H_
+
+#include <string>
+
+namespace chromeos {
+namespace file_system_provider {
+
+class ProvidedFileSystem;
+
+// Observes file_system_provider::Service for mounting and unmounting events.
+class Observer {
+ public:
+  // Called when a provided |file_system| is registered successfully.
+  virtual void OnProvidedFileSystemRegistered(
+      const ProvidedFileSystem& file_system) = 0;
+
+  // Called when a provided |file_system| is unregistered successfully.
+  virtual void OnProvidedFileSystemUnregistered(
+      const ProvidedFileSystem& file_system) = 0;
+};
+
+}  // namespace file_system_provider
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_OBSERVER_H_