Tab dragging as implemented as a mus API.

components/mus/public/cpp/window_manager_delegate.h

Index: components/mus/public/cpp/window_manager_delegate.h
diff --git a/components/mus/public/cpp/window_manager_delegate.h b/components/mus/public/cpp/window_manager_delegate.h
index 99ddf34cc4e10daae412fa917ebd078bebe9c909..9e41bbd96d0df53575368e9485a333f063d2b0af 100644
--- a/components/mus/public/cpp/window_manager_delegate.h
+++ b/components/mus/public/cpp/window_manager_delegate.h
@@ -16,6 +16,7 @@
 #include "components/mus/public/interfaces/cursor.mojom.h"
 #include "components/mus/public/interfaces/event_matcher.mojom.h"
 #include "components/mus/public/interfaces/window_manager_constants.mojom.h"
+#include "components/mus/public/interfaces/window_tree_constants.mojom.h"
 #include "ui/events/mojo/event.mojom.h"
 
 namespace display {
@@ -107,6 +108,14 @@ class WindowManagerDelegate {
 
   virtual void OnAccelerator(uint32_t id, const ui::Event& event) = 0;
 
+  virtual void OnWmPerformMoveLoop(
+      Window* window,
+      ::mus::mojom::MoveLoopSource source,
+      const gfx::Point& cursor_location,
+      const base::Callback<void(bool)>& on_done) = 0;
+
+  virtual void OnWmCancelMoveLoop(Window* window) = 0;
+
  protected:
   virtual ~WindowManagerDelegate() {}
 };