Provide lazy CommitPendingWrites in addition to eager SavePersistentPrefs.

chrome/common/persistent_pref_store.h

Index: chrome/common/persistent_pref_store.h
diff --git a/chrome/common/persistent_pref_store.h b/chrome/common/persistent_pref_store.h
index c79d6783d8a11f24259b04b9fec1722bad771887..35d441c7bf2c101e72b4c55462e18052b2a9a8b2 100644
--- a/chrome/common/persistent_pref_store.h
+++ b/chrome/common/persistent_pref_store.h
@@ -10,6 +10,8 @@
 
 #include <chrome/common/pref_store.h>
 
+class NotificationSource;
+
 // This interface is complementary to the PrefStore interface, declaring
 // additional functionality that adds support for setting values and persisting
 // the data to some backing store.
@@ -67,6 +69,12 @@ class PersistentPrefStore : public PrefStore {
 
   // Schedules an asynchronous write operation.
   virtual void ScheduleWritePrefs() = 0;
+
+  // Lands any pending writes to disk.
+  virtual void CommitPendingWrite() = 0;
+
+  // Sets source to use for PREF_COMMITTED notification.
+  virtual void SetNotificationSource(const NotificationSource& source) = 0;
 };
 
 #endif  // CHROME_COMMON_PERSISTENT_PREF_STORE_H_