Replace more ObserverList with base::ObserverList.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 3101bc21e0190061f4ac930d3ac9fa75b07a5057..e82c49dbe42699fad7c4ee815443fa475310748d 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -334,8 +334,8 @@ class COMPOSITOR_EXPORT Compositor
   // The root of the Layer tree drawn by this compositor.
   Layer* root_layer_;
 
-  ObserverList<CompositorObserver, true> observer_list_;
-  ObserverList<CompositorAnimationObserver> animation_observer_list_;
+  base::ObserverList<CompositorObserver, true> observer_list_;
+  base::ObserverList<CompositorAnimationObserver> animation_observer_list_;
   std::list<CompositorBeginFrameObserver*> begin_frame_observer_list_;
 
   gfx::AcceleratedWidget widget_;