Replace more ObserverList with base::ObserverList.

ui/aura/window.cc

Index: ui/aura/window.cc
diff --git a/ui/aura/window.cc b/ui/aura/window.cc
index 69bddfdc77219efb3630e5455df8d1975138c1df..1e293b72343b994b81641e0f7570d74d2105ce0c 100644
--- a/ui/aura/window.cc
+++ b/ui/aura/window.cc
@@ -197,7 +197,7 @@ Window::Window(WindowDelegate* delegate)
       // Don't notify newly added observers during notification. This causes
       // problems for code that adds an observer as part of an observer
       // notification (such as the workspace code).
-      observers_(ObserverList<WindowObserver>::NOTIFY_EXISTING_ONLY) {
+      observers_(base::ObserverList<WindowObserver>::NOTIFY_EXISTING_ONLY) {
   set_target_handler(delegate_);
 }