Tab dragging as implemented as a mus API.

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index 3f11af23b86cb72b530d135b27f477c807baf898..dcb8f87b8e5c2eac92ebd08e847e1d2f4ce8fda0 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -241,5 +241,17 @@ void WindowManager::OnAccelerator(uint32_t id, const ui::Event& event) {
   }
 }
 
+void WindowManager::OnWmPerformMoveLoop(
+    ::ui::Window* window,
+    ::ui::mojom::MoveLoopSource source,
+    const gfx::Point& cursor_location,
+    const base::Callback<void(bool)>& on_done) {
+  NOTIMPLEMENTED();
+}
+
+void WindowManager::OnWmCancelMoveLoop(::ui::Window* window) {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace mus
 }  // namespace ash