Remove stl_util's STLDeleteContainerPairSecondPointers.

components/syncable_prefs/pref_model_associator.h

Index: components/syncable_prefs/pref_model_associator.h
diff --git a/components/syncable_prefs/pref_model_associator.h b/components/syncable_prefs/pref_model_associator.h
index 8938d14381eadf8e94f6251e908c1acb0e2f7d1a..8df666206b153f14da0b0bd3b46f419249e1191f 100644
--- a/components/syncable_prefs/pref_model_associator.h
+++ b/components/syncable_prefs/pref_model_associator.h
@@ -190,9 +190,9 @@ class PrefModelAssociator
   // Map prefs to lists of observers. Observers will receive notification when
   // a pref changes, including the detail of whether or not the change came
   // from sync.
-  typedef base::ObserverList<SyncedPrefObserver> SyncedPrefObserverList;
-  typedef base::hash_map<std::string, SyncedPrefObserverList*>
-      SyncedPrefObserverMap;
+  using SyncedPrefObserverList = base::ObserverList<SyncedPrefObserver>;
+  using SyncedPrefObserverMap =
+      base::hash_map<std::string, std::unique_ptr<SyncedPrefObserverList>>;
 
   void NotifySyncedPrefObservers(const std::string& path, bool from_sync) const;