Provide lazy CommitPendingWrites in addition to eager SavePersistentPrefs.

chrome/common/json_pref_store.h

Index: chrome/common/json_pref_store.h
diff --git a/chrome/common/json_pref_store.h b/chrome/common/json_pref_store.h
index d5970b95f948d5a1214319ae9d56eb52ab35ed51..8f1cbd78980d4ca6fa4ecd49258a631716ca0dbe 100644
--- a/chrome/common/json_pref_store.h
+++ b/chrome/common/json_pref_store.h
@@ -1,4 +1,4 @@
-// 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.
 
@@ -46,6 +46,7 @@ class JsonPrefStore : public PersistentPrefStore,
   virtual PrefReadError ReadPrefs();
   virtual bool WritePrefs();
   virtual void ScheduleWritePrefs();
+  virtual void CommitPendingWrite();
   // TODO(battre) remove this function
   virtual void ReportValueChanged(const std::string& key);