GTTF: Add missing virtual destructors.

base/prefs/public/pref_change_registrar.h

Index: base/prefs/public/pref_change_registrar.h
diff --git a/base/prefs/public/pref_change_registrar.h b/base/prefs/public/pref_change_registrar.h
index 84df6526696b0eb82fc764504bf0b06791ccd721..6d93e5e2b198bc010f46aec119a02c8d0b986108 100644
--- a/base/prefs/public/pref_change_registrar.h
+++ b/base/prefs/public/pref_change_registrar.h
@@ -19,7 +19,8 @@ class PrefServiceBase;
 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
 // manages observers of preference changes. When the Registrar is destroyed,
 // all registered observers are automatically unregistered with the PrefStore.
-class BASE_PREFS_EXPORT PrefChangeRegistrar : public PrefObserver {
+class BASE_PREFS_EXPORT PrefChangeRegistrar
+    : public NON_EXPORTED_BASE(PrefObserver) {
  public:
   // You can register this type of callback if you need to know the
   // path of the preference that is changing.