Fix css cut-off issue on cell mini-toolbar (#1287)
Fix css cut-off issue on cell mini-toolbar (#1287)

* fix css cut-off issue on cell mini-toolbar

googledatalab/datalab,googledatalab/datalab,yebrahim/datalab,googledatalab/datalab,craigcitro/datalab,craigcitro/datalab,googledatalab/datalab,yebrahim/datalab,googledatalab/datalab,craigcitro/datalab,yebrahim/datalab,craigcitro/datalab,parthea/datalab,yebrahim/datalab,googledatalab/datalab,parthea/datalab,parthea/datalab,parthea/datalab,parthea/datalab,parthea/datalab,yebrahim/datalab,craigcitro/datalab