Tab dragging as implemented as a mus API.

services/ui/demo/mus_demo.h

Index: services/ui/demo/mus_demo.h
diff --git a/services/ui/demo/mus_demo.h b/services/ui/demo/mus_demo.h
index 42e086d1f0d9f85566c50be5bed1be392c07ad64..cbc9f0d2677e1e1c81fdf13c3353904d53b4e3b2 100644
--- a/services/ui/demo/mus_demo.h
+++ b/services/ui/demo/mus_demo.h
@@ -60,6 +60,11 @@ class MusDemo : public shell::Service,
   void OnWmNewDisplay(ui::Window* window,
                       const display::Display& display) override;
   void OnAccelerator(uint32_t id, const ui::Event& event) override;
+  void OnWmPerformMoveLoop(ui::Window* window,
+                           ui::mojom::MoveLoopSource source,
+                           const gfx::Point& cursor_location,
+                           const base::Callback<void(bool)>& on_done) override;
+  void OnWmCancelMoveLoop(ui::Window* window) override;
 
   // Allocate a bitmap the same size as the window to draw into.
   void AllocBitmap();