message: fix tooltip for bmap
diff: @@ -114,6 +114,16 @@ define(function (require) {
  return this._viewport;
  },
  + getViewportRootOffset: function () {
  + var viewportRoot = this.getViewportRoot();
  + if (viewportRoot) {
  + return {
  + offsetLeft: viewportRoot.offsetLeft || 0,
  + offsetTop: viewportRoot.offsetTop || 0
  + };
  + }
  + },
  +
  refresh: function () {
  var list = this.storage.getDisplayList(true);
  