Revert of Refactor backdrop

ash/test/workspace_controller_test_api.cc

Index: ash/test/workspace_controller_test_api.cc
diff --git a/ash/test/workspace_controller_test_api.cc b/ash/test/workspace_controller_test_api.cc
index ecc54aff0564651c337f77b86124af141e9005f8..ffd6e7c5b8737e039063586de115f378e5be1b66 100644
--- a/ash/test/workspace_controller_test_api.cc
+++ b/ash/test/workspace_controller_test_api.cc
@@ -5,8 +5,6 @@
 #include "ash/test/workspace_controller_test_api.h"
 
 #include "ash/test/workspace_event_handler_test_helper.h"
-#include "ash/wm/workspace/backdrop_controller.h"
-#include "ash/wm/workspace/workspace_layout_manager.h"
 #include "ash/wm/workspace_controller.h"
 #include "ui/aura/window.h"
 
@@ -28,9 +26,5 @@
   return WorkspaceEventHandlerTestHelper(GetEventHandler()).resize_controller();
 }
 
-aura::Window* WorkspaceControllerTestApi::GetBackdropWindow() {
-  return controller_->layout_manager_->backdrop_controller_->backdrop_window_;
-}
-
 }  // namespace test
 }  // namespace ash