Make ui::Compositor BeginFrame subscription robust

ui/compositor/compositor.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
-#include <list>
 #include <string>
 
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/surfaces/surface_sequence.h"
@@ skipping 318 matching lines @@
 
   gfx::Size size_;
 
   ui::ContextFactory* context_factory_;
 
   // The root of the Layer tree drawn by this compositor.
   Layer* root_layer_;
 
   base::ObserverList<CompositorObserver, true> observer_list_;
   base::ObserverList<CompositorAnimationObserver> animation_observer_list_;
-  std::list<CompositorBeginFrameObserver*> begin_frame_observer_list_;
+  base::ObserverList<CompositorBeginFrameObserver, true>
+      begin_frame_observer_list_;
 
   gfx::AcceleratedWidget widget_;
   bool widget_valid_;
   bool output_surface_requested_;
   scoped_ptr<cc::SurfaceIdAllocator> surface_id_allocator_;
   scoped_refptr<cc::Layer> root_web_layer_;
   scoped_ptr<cc::LayerTreeHost> host_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   // The manager of vsync parameters for this compositor.
@@ skipping 15 matching lines @@
   cc::BeginFrameArgs missed_begin_frame_args_;
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_