Provide lazy CommitPendingWrites in addition to eager SavePersistentPrefs.

chrome/common/json_pref_store.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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_COMMON_JSON_PREF_STORE_H_
 #define CHROME_COMMON_JSON_PREF_STORE_H_
 #pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 10 matching lines @@
 class DictionaryValue;
 class FilePath;
 class Value;
 
 // A writable PrefStore implementation that is used for user preferences.
 class JsonPrefStore : public PersistentPrefStore,
                       public ImportantFileWriter::DataSerializer {
  public:
   // |file_message_loop_proxy| is the MessageLoopProxy for a thread on which
   // file I/O can be done.
+  // |source| is source to be used for sending PREF_COMMMITTED notification.
   JsonPrefStore(const FilePath& pref_filename,
                 base::MessageLoopProxy* file_message_loop_proxy);
   virtual ~JsonPrefStore();
 
   // PrefStore overrides:
   virtual ReadResult GetValue(const std::string& key, Value** result) const;
   virtual void AddObserver(PrefStore::Observer* observer);
   virtual void RemoveObserver(PrefStore::Observer* observer);
 
   // PersistentPrefStore overrides:
   virtual void SetValue(const std::string& key, Value* value);
   virtual void SetValueSilently(const std::string& key, Value* value);
   virtual void RemoveValue(const std::string& key);
   virtual bool ReadOnly() const;
   virtual PrefReadError ReadPrefs();
   virtual bool WritePrefs();
   virtual void ScheduleWritePrefs();
+  virtual void CommitPendingWrite();
+  void SetNotificationSource(const NotificationSource& source);

[Mattias Nissler (ping if slow), 2011/03/23 15:12:37]

This is not well-defined. Note that a PrefStore can be hooked up to multiple
PrefServices, thus pushing a source down and sending the notification from there
is not a good idea.

Note that PrefStore already has an observer interface to you could use to
propagate the notification back up. Why not add your stuff there?

We have invested considerable time recently to detangle all Pref classes. One of
the goals was to concentrate sending notifications in PrefNotifierImpl, and your
CL adds back in a notification from deep within the pref system, which we like
to avoid since it decouples the innards of the implementation from the
interface, which is implemented in PrefService.

   // TODO(battre) remove this function
   virtual void ReportValueChanged(const std::string& key);
 
  private:
   // ImportantFileWriter::DataSerializer overrides:
   virtual bool SerializeData(std::string* output);
 
   FilePath path_;
 
   scoped_ptr<DictionaryValue> prefs_;
 
   bool read_only_;
 
   // Helper for safely writing pref data.
   ImportantFileWriter writer_;
 
+  // Source for PREF_COMMITTED notification.
+  NotificationSource source_;
+
   ObserverList<PrefStore::Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 };
 
 #endif  // CHROME_COMMON_JSON_PREF_STORE_H_