Pull request #2986: JSY-21565 fix: popover拖拽定位问题

Merge in VISUAL/fineui from ~KIRA/fineui:master to master

* commit '83dc71cc287895a2335ff99bb7932dc317a644b7':
  JSY-21565 fix: popover拖拽定位问题

src/base/layer/layer.popover.js

@@ -158,9 +158,8 @@ BI.Popover = BI.inherit(BI.Widget, {
     mounted: function () {
         var self = this;
         this.dragger.element.mousedown(function (e) {
-            var pos = self.element.offset();
-            self.startX = pos.left;
-            self.startY = pos.top;
+            self.startX = self.element[0].offsetLeft;
+            self.startY = self.element[0].offsetTop;
             self.tracker.captureMouseMoves(e);
         });
     },