Remove PrefServiceSimple, replacing it with PrefService and PrefRegistrySimple.

chrome/browser/prefs/pref_service.cc

Index: chrome/browser/prefs/pref_service.cc
diff --git a/chrome/browser/prefs/pref_service.cc b/chrome/browser/prefs/pref_service.cc
index 61f54f7f1f36acdf5ca20d96b01ae0cc27764c2c..87f2d219e7a51f3bec1535ce895a483444a4543b 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -345,6 +345,10 @@ void PrefService::UnregisterPreference(const char* path) {
   default_store_->RemoveDefaultValue(path);
 }
 
+bool PrefService::AllowPrefRegistrarSimple() const {
+  return true;
+}
+
 void PrefService::ClearPref(const char* path) {
   DCHECK(CalledOnValidThread());