Remove usage of base::ObserverList<T>::Iter::GetNext() in //components/prefs.

components/prefs/pref_notifier_impl_unittest.cc

Index: components/prefs/pref_notifier_impl_unittest.cc
diff --git a/components/prefs/pref_notifier_impl_unittest.cc b/components/prefs/pref_notifier_impl_unittest.cc
index 517a403936aaed88da382d4d1ec0a561f978dc80..06ab053045c5e02198741708edcd13b59794c1fb 100644
--- a/components/prefs/pref_notifier_impl_unittest.cc
+++ b/components/prefs/pref_notifier_impl_unittest.cc
@@ -59,12 +59,9 @@ class MockPrefNotifier : public PrefNotifierImpl {
     if (observer_iterator == pref_observers()->end())
       return false;
 
-    PrefObserverList* observer_list = observer_iterator->second.get();
-    PrefObserverList::Iterator it(observer_list);
-    PrefObserver* existing_obs;
     size_t count = 0;
-    while ((existing_obs = it.GetNext()) != NULL) {
-      if (existing_obs == obs)
+    for (auto& existing_obs : *observer_iterator->second) {
+      if (&existing_obs == obs)
         count++;
     }