Merges RootWindowControllerCommon into WmRootWindowController

ash/common/wm/maximize_mode/maximize_mode_window_manager.cc

Index: ash/common/wm/maximize_mode/maximize_mode_window_manager.cc
diff --git a/ash/common/wm/maximize_mode/maximize_mode_window_manager.cc b/ash/common/wm/maximize_mode/maximize_mode_window_manager.cc
index b15ec13aedd64c2911a81db942dc40e46a5746fe..2c3b5cf90920e2d6cb770afe9efb534428fd0edb 100644
--- a/ash/common/wm/maximize_mode/maximize_mode_window_manager.cc
+++ b/ash/common/wm/maximize_mode/maximize_mode_window_manager.cc
@@ -14,6 +14,7 @@
 #include "ash/common/wm/overview/window_selector_controller.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/common/wm/wm_event.h"
+#include "ash/common/wm/workspace_controller.h"
 #include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
@@ -319,8 +320,9 @@ void MaximizeModeWindowManager::EnableBackdropBehindTopWindowOnEachDisplay(
     WmRootWindowController* controller = root->GetRootWindowController();
     WmWindow* default_container =
         root->GetChildByShellWindowId(kShellWindowId_DefaultContainer);
-    controller->SetMaximizeBackdropDelegate(base::WrapUnique(
-        enable ? new WorkspaceBackdropDelegate(default_container) : nullptr));
+    controller->workspace_controller()->SetMaximizeBackdropDelegate(
+        enable ? base::MakeUnique<WorkspaceBackdropDelegate>(default_container)
+               : nullptr);
   }
 }