mus: Use the new drag API to implement tab dragging in chrome.

ash/mus/window_manager.h

Index: ash/mus/window_manager.h
diff --git a/ash/mus/window_manager.h b/ash/mus/window_manager.h
index e97de409f67b25749d1b46c52f30bd6ad7cfbe28..a05b8aa5ac00257a452ae6381a0ac3c3ce86890f 100644
--- a/ash/mus/window_manager.h
+++ b/ash/mus/window_manager.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <set>
 
+#include "ash/common/wm/wm_toplevel_window_event_handler.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "components/mus/common/types.h"
@@ -66,6 +67,9 @@ class WindowManager : public ::mus::WindowManagerDelegate,
   ::mus::Window* NewTopLevelWindow(
       std::map<std::string, std::vector<uint8_t>>* properties);
 
+  // Called from WmMoveLoop to delete the object.
+  void OnWmMoveLoopCompleted(uint32_t change_id, bool succeeded);
+
   std::set<RootWindowController*> GetRootWindowControllers();
 
   void AddRootWindowsObserver(RootWindowsObserver* observer);