popup展示时autoPan卡顿，速度慢

* **L7 Version**: 2.15.2
* **Platform**: windows11 chrome 112.0.5615.138
* **Mini Showcase(like screenshots)**:
* **CodePen Link**:

popup展示时autoPan卡顿，速度慢，有时候20秒动画都无法完成，请教是什么问题？地图拖拽挺流畅的，应该不是性能问题。

Start by reproducing the popup autoPan lag with L7 2.15.2 on Windows 11 in Chrome 112, using the issue's description as the only scenario. Trace the popup autoPan implementation and identify why the animation can take about 20 seconds; done means the popup pans smoothly and the behavior is covered by a regression test.

Written by the indexing model from the issue text.