Add {Lock,Unlock,Show,Hide}Cursor() to the window manager mojom.

ui/aura/mus/window_tree_client.h

Index: ui/aura/mus/window_tree_client.h
diff --git a/ui/aura/mus/window_tree_client.h b/ui/aura/mus/window_tree_client.h
index de030c3dda342dd8265a60072255735945c0933a..f85a3702320bcf8b9229e3d874ebffc10d1877d5 100644
--- a/ui/aura/mus/window_tree_client.h
+++ b/ui/aura/mus/window_tree_client.h
@@ -475,6 +475,11 @@ class AURA_EXPORT WindowTreeClient
   void RemoveActivationParent(Window* window) override;
   void ActivateNextWindow() override;
   void SetExtendedHitArea(Window* window, const gfx::Insets& hit_area) override;
+  void LockCursor() override;
+  void UnlockCursor() override;
+  void ShowCursor() override;
+  void HideCursor() override;
+  void SetGlobalOverrideCursor(base::Optional<ui::CursorData> cursor) override;
   void RequestClose(Window* window) override;
   bool WaitForInitialDisplays() override;
   WindowTreeHostMusInitParams CreateInitParamsForNewDisplay() override;