Remove the singleton instance get/delete methods from RootWindow (yay)

ui/aura/root_window.h

Index: ui/aura/root_window.h
===================================================================
--- ui/aura/root_window.h	(revision 124527)
+++ ui/aura/root_window.h	(working copy)
@@ -50,8 +50,8 @@
                                public internal::FocusManager,
                                public ui::LayerAnimationObserver {
  public:
-  static RootWindow* GetInstance();
-  static void DeleteInstance();
+  RootWindow();
+  virtual ~RootWindow();
 
   static void set_use_fullscreen_host_window(bool use_fullscreen) {
     use_fullscreen_host_window_ = use_fullscreen;
@@ -200,9 +200,6 @@
  private:
   friend class Window;
 
-  RootWindow();
-  virtual ~RootWindow();
-
   // Called whenever the mouse moves, tracks the current |mouse_moved_handler_|,
   // sending exited and entered events as its value changes.
   void HandleMouseMoved(const MouseEvent& event, Window* target);