Tab dragging as implemented as a mus API.

components/mus/ws/window_manager_state.h

Index: components/mus/ws/window_manager_state.h
diff --git a/components/mus/ws/window_manager_state.h b/components/mus/ws/window_manager_state.h
index dca6670d400ac522e3b2bc62821babc653840a3f..8ab6bd181bd29ac6e2f2e534c4e9d04569a25da3 100644
--- a/components/mus/ws/window_manager_state.h
+++ b/components/mus/ws/window_manager_state.h
@@ -56,6 +56,15 @@ class WindowManagerState : public EventDispatcherDelegate {
     return event_dispatcher_.capture_window();
   }
 
+  //
+  void StartMoveLoop(uint32_t change_id, WindowId window_id,

[sky, 2016/06/24 19:59:01]

In general only the functions from clients use a WindowId, the rest of the code
passes around ServerWindow. For example, SetCapture on line 53 takes the
ServerWindow, not the WindowId.

+                     const gfx::Rect& revert_bounds);
+  void EndMoveLoop();
+  uint32_t GetCurrentMoveLoopChangeId();
+  WindowId GetCurrentMoveLoopWindowId();
+  gfx::Rect GetCurrentMoveLoopRevertBounds();
+  bool in_move_loop() { return !!current_move_loop_.get(); }
+
   void ReleaseCaptureBlockedByModalWindow(const ServerWindow* modal_window);
   void ReleaseCaptureBlockedByAnyModalWindow();
 
@@ -80,6 +89,7 @@ class WindowManagerState : public EventDispatcherDelegate {
   void OnEventAck(mojom::WindowTree* tree, mojom::EventResult result);
 
  private:
+  struct CurrentMoveLoopState;
   class ProcessedEventTarget;
   friend class Display;
   friend class test::WindowManagerStateTestApi;
@@ -166,6 +176,7 @@ class WindowManagerState : public EventDispatcherDelegate {
   base::WeakPtr<Accelerator> post_target_accelerator_;
   std::queue<std::unique_ptr<QueuedEvent>> event_queue_;
   base::OneShotTimer event_ack_timer_;
+  std::unique_ptr<CurrentMoveLoopState> current_move_loop_;
 
   EventDispatcher event_dispatcher_;