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

ui/compositor/layer_animator.cc

Index: ui/compositor/layer_animator.cc
diff --git a/ui/compositor/layer_animator.cc b/ui/compositor/layer_animator.cc
index 5af6fb6ae5c04a825d96fe7044288a0458cfaec7..87b852ecf93b2557040aa3e19334af0e5cbacf1c 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -872,13 +872,8 @@ void LayerAnimator::GetTargetValue(
 }
 
 void LayerAnimator::OnScheduled(LayerAnimationSequence* sequence) {
-  if (observers_.might_have_observers()) {
-    base::ObserverListBase<LayerAnimationObserver>::Iterator it(&observers_);
-    LayerAnimationObserver* obs;
-    while ((obs = it.GetNext()) != NULL) {
-      sequence->AddObserver(obs);
-    }
-  }
+  for (LayerAnimationObserver& observer : observers_)
+    sequence->AddObserver(&observer);
   sequence->OnScheduled();
 }