Tab dragging as implemented as a mus API.

components/mus/ws/window_server.cc

Index: components/mus/ws/window_server.cc
diff --git a/components/mus/ws/window_server.cc b/components/mus/ws/window_server.cc
index fb6382f70af6b419a8609bba214aaa10a441d3d5..54d413a2def06cf4f3695a48254dc57d7b014a62 100644
--- a/components/mus/ws/window_server.cc
+++ b/components/mus/ws/window_server.cc
@@ -312,6 +312,24 @@ void WindowServer::WindowManagerCreatedTopLevelWindow(
                                              change.client_change_id, window);
 }
 
+void WindowServer::WindowManagerCompletedMoveLoop(
+    uint32_t window_manager_change_id,
+    const ServerWindow* window,
+    bool completed) {
+  InFlightWindowManagerChange change;
+  if (!GetAndClearInFlightWindowManagerChange(window_manager_change_id,
+                                              &change)) {
+    return;
+  }
+  if (!window) {
+    WindowManagerSentBogusMessage();
+    return;
+  }
+
+  WindowTree* tree = GetTreeWithId(change.client_id);
+  tree->OnMoveLoopCompleted(change.client_change_id, completed);
+}
+
 void WindowServer::ProcessWindowBoundsChanged(const ServerWindow* window,
                                               const gfx::Rect& old_bounds,
                                               const gfx::Rect& new_bounds) {