JSY-21565 fix: popover拖拽定位问题

src/base/layer/layer.popover.js

@@ -159,9 +159,8 @@ BI.Popover = BI.inherit(BI.Widget, {
         var self = this;
         var o = this.options;
         this.dragger.element.mousedown(function (e) {
-            var pos = self.element.offset();
+            self.startX = self.element[0].offsetLeft;
-            self.startX = pos.left;
+            self.startY = self.element[0].offsetTop;
-            self.startY = pos.top;
             self.tracker.captureMouseMoves(e);
         });
     },