Replace base::CallbackList with base::ObserverList in CastConfigDelegate

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 24f61767090e414aa068c0a0f894352539729437..0a0910250e80208f675d8f8b129d34b329a1563d 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -607,6 +607,9 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   // Initializes the root window so that it can host browser windows.
   void InitRootWindow(aura::Window* root_window);
 
+  // Hides the shelf view if any are visible.
+  void HideShelf();
+
   // ash::SystemModalContainerEventFilterDelegate overrides:
   bool CanWindowReceiveEvents(aura::Window* window) override;