Add destroy that we can call from different places
Add destroy that we can call from different places

cc: da39a3ee5e6b4b0d3255bfef95601890afd80709@zeningqu

uwdata/vega-lite-ui,vega/vega-lite-ui,uwdata/vega-lite-ui,vega/vega-lite-ui,vega/vega-lite-ui,uwdata/vega-lite-ui