Converts MaximizeModeWindowManager to use ash/common types

ash/mus/bridge/wm_root_window_controller_mus.h

Index: ash/mus/bridge/wm_root_window_controller_mus.h
diff --git a/ash/mus/bridge/wm_root_window_controller_mus.h b/ash/mus/bridge/wm_root_window_controller_mus.h
index abc0a87d953e4e153b9e40839a14ed3f86351dae..aaca3485cdd8940ac4e39165b54dc63f2ec7ac33 100644
--- a/ash/mus/bridge/wm_root_window_controller_mus.h
+++ b/ash/mus/bridge/wm_root_window_controller_mus.h
@@ -55,6 +55,9 @@ class WmRootWindowControllerMus : public WmRootWindowController {
   bool HasShelf() override;
   WmShell* GetShell() override;
   wm::WorkspaceWindowState GetWorkspaceWindowState() override;
+  void SetMaximizeBackdropDelegate(
+      std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate)
+      override;
   AlwaysOnTopController* GetAlwaysOnTopController() override;
   WmShelf* GetShelf() override;
   WmWindow* GetWindow() override;