Tab dragging as implemented as a mus API.

components/mus/ws/window_server.h

Index: components/mus/ws/window_server.h
diff --git a/components/mus/ws/window_server.h b/components/mus/ws/window_server.h
index 0ecbc76ee4cbf90554d5794dc7343d3c4b88b1b4..9297ae8773db8b3dbf37f82079513570c02872d4 100644
--- a/components/mus/ws/window_server.h
+++ b/components/mus/ws/window_server.h
@@ -158,6 +158,9 @@ class WindowServer : public ServerWindowDelegate,
   void WindowManagerCreatedTopLevelWindow(WindowTree* wm_tree,
                                           uint32_t window_manager_change_id,
                                           const ServerWindow* window);
+  void WindowManagerCompletedMoveLoop(uint32_t window_manager_change_id,
+                                      const ServerWindow* window,
+                                      bool completed);
 
   // Called when we get an unexpected message from the WindowManager.
   // TODO(sky): decide what we want to do here.
@@ -196,7 +199,19 @@ class WindowServer : public ServerWindowDelegate,
   // a [re]paint. This should only be called in a test configuration.
   void SetPaintCallback(const base::Callback<void(ServerWindow*)>& callback);
 
+  void StartMoveLoop(uint32_t change_id,
+                     ServerWindow* window,
+                     WindowTree* initiator,
+                     const gfx::Rect& revert_bounds);
+  void EndMoveLoop();
+  uint32_t GetCurrentMoveLoopChangeId();
+  ServerWindow* GetCurrentMoveLoopWindow();
+  WindowTree* GetCurrentMoveLoopInitiator();
+  gfx::Rect GetCurrentMoveLoopRevertBounds();
+  bool in_move_loop() { return !!current_move_loop_.get(); }

[sky, 2016/06/29 00:04:09]

nit: const

+
  private:
+  struct CurrentMoveLoopState;
   friend class Operation;
 
   using WindowTreeMap =
@@ -311,6 +326,8 @@ class WindowServer : public ServerWindowDelegate,
 
   std::unique_ptr<DisplayManager> display_manager_;
 
+  std::unique_ptr<CurrentMoveLoopState> current_move_loop_;
+
   // Set of WindowTrees.
   WindowTreeMap tree_map_;