Ports SystemModalContainerLayoutManager to ash/common

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index efda39b1fb9230da7336410c723d82ba68709484..16d281deea9c0653ef7359b04b8a3dae8cba7f1c 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -150,16 +150,6 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
   // True if the window can receive events on this root window.
   bool CanWindowReceiveEvents(aura::Window* window);
 
-  // Returns the layout-manager for the appropriate modal-container. If the
-  // window is inside the lockscreen modal container, then the layout manager
-  // for that is returned. Otherwise the layout manager for the default modal
-  // container is returned.
-  // If no window is specified (i.e. |window| is NULL), then the lockscreen
-  // modal container is used if the screen is currently locked. Otherwise, the
-  // default modal container is used.
-  SystemModalContainerLayoutManager* GetSystemModalLayoutManager(
-      aura::Window* window);
-
   aura::Window* GetContainer(int container_id);
   const aura::Window* GetContainer(int container_id) const;