Provide lazy CommitPendingWrites in addition to eager SavePersistentPrefs.

chrome/browser/prefs/overlay_persistent_pref_store.cc

Index: chrome/browser/prefs/overlay_persistent_pref_store.cc
diff --git a/chrome/browser/prefs/overlay_persistent_pref_store.cc b/chrome/browser/prefs/overlay_persistent_pref_store.cc
index 69390255ee77b21e480861d5de340d7252a394a9..229dd0d37392a339aea62669090ca08947f92e4a 100644
--- a/chrome/browser/prefs/overlay_persistent_pref_store.cc
+++ b/chrome/browser/prefs/overlay_persistent_pref_store.cc
@@ -70,6 +70,15 @@ void OverlayPersistentPrefStore::ScheduleWritePrefs() {
   // We do not write intentionally.
 }
 
+void OverlayPersistentPrefStore::CommitPendingWrite() {
+  // We do not write intentionally.
+}
+
+void OverlayPersistentPrefStore::SetNotificationSource(
+    const NotificationSource& source) {
+  // We do not care about PREF_COMMITTED notification and its source.
+}
+
 void OverlayPersistentPrefStore::ReportValueChanged(const std::string& key) {
   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 }