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 3be7ba8a1dee8a33e9aca00f3fa46e8ac4e5b951..0bfdfdd454366b9386fd10cb4d1e4d5d8b667110 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -240,5 +240,17 @@ void WindowManager::OnAccelerator(uint32_t id, const ui::Event& event) {
   }
 }
 
+void WindowManager::OnWmPerformMoveLoop(
+    ::mus::Window* window,
+    ::mus::mojom::MoveLoopSource source,
+    const gfx::Point& cursor_location,
+    const base::Callback<void(bool)>& on_done) {
+  NOTIMPLEMENTED();
+}
+
+void WindowManager::OnWmCancelMoveLoop(::mus::Window* window) {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace mus
 }  // namespace ash