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..20eec6532ae50f8045b92afc801e7b54760f46c6 100644
--- a/chrome/browser/prefs/overlay_persistent_pref_store.cc
+++ b/chrome/browser/prefs/overlay_persistent_pref_store.cc
@@ -70,6 +70,10 @@ void OverlayPersistentPrefStore::ScheduleWritePrefs() {
   // We do not write intentionally.
 }
 
+void OverlayPersistentPrefStore::CommitPendingWrites() {
+  // We do not write intentionally.
+}
+
 void OverlayPersistentPrefStore::ReportValueChanged(const std::string& key) {
   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 }