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

ui/aura/test/aura_test_base.h

Index: ui/aura/test/aura_test_base.h
===================================================================
--- ui/aura/test/aura_test_base.h	(revision 124527)
+++ ui/aura/test/aura_test_base.h	(working copy)
@@ -30,11 +30,11 @@
  protected:
   void RunAllPendingInMessageLoop();
 
-  RootWindow* root_window() { return root_window_; }
+  RootWindow* root_window() { return root_window_.get(); }
 
  private:
   AuraTestHelper helper_;
-  RootWindow* root_window_;
+  scoped_ptr<RootWindow> root_window_;
   scoped_ptr<TestStackingClient> stacking_client_;
 
   DISALLOW_COPY_AND_ASSIGN(AuraTestBase);