Tab dragging as implemented as a mus API.

components/mus/ws/window_tree.h

Index: components/mus/ws/window_tree.h
diff --git a/components/mus/ws/window_tree.h b/components/mus/ws/window_tree.h
index 0e804f355a116e70aeecc3cb1e81222f50cb526b..ee724ccedde5ee3cc5fbd29f8fa4ad1a9d077fe5 100644
--- a/components/mus/ws/window_tree.h
+++ b/components/mus/ws/window_tree.h
@@ -405,6 +405,11 @@ class WindowTree : public mojom::WindowTree,
       override;
   void GetCursorLocationMemory(const GetCursorLocationMemoryCallback& callback)
       override;
+  void PerformWindowMove(uint32_t change_id,
+                         Id window_id,
+                         ::mus::mojom::MoveLoopSource source,
+                         const gfx::Point& cursor) override;
+  void CancelWindowMove(Id window_id) override;
 
   // mojom::WindowManagerClient:
   void AddAccelerator(uint32_t id,
@@ -427,6 +432,7 @@ class WindowTree : public mojom::WindowTree,
                             mojom::Cursor cursor_id) override;
   void OnWmCreatedTopLevelWindow(uint32_t change_id,
                                  Id transport_window_id) override;
+  void OnWmMoveLoopCompleted(uint32_t change_id, bool succeeded) override;
 
   // AccessPolicyDelegate:
   bool HasRootForAccessPolicy(const ServerWindow* window) const override;