[fsp] Store observed entries in preferences.

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>
 
@@ skipping 33 matching lines @@
   // call the callback, the tag will be updated and OnObservedEntryTagUpdated
   // called. The reference to |child_changes| is valid at least as long as
   // |callback|.
   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.
+  // Called after the tag value is updated for the observed entry.
   virtual void OnObservedEntryTagUpdated(
       const ProvidedFileSystemInfo& file_system_info,
       const base::FilePath& observed_path,
       const std::string& tag) = 0;
 
-  // Called when list of observed entries is changed.
+  // Called after the list of observed entries is changed.
   virtual void OnObservedEntryListChanged(
       const ProvidedFileSystemInfo& file_system_info,
       const ObservedEntries& observed_entries) = 0;
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_OBSERVER_H_