easy `_resizeStartDiff` linearly to 0 as user drags
easy `_resizeStartDiff` linearly to 0 as user drags

softwords/plottable,RobertoMalatesta/plottable,NextTuesday/plottable,RobertoMalatesta/plottable,gdseller/plottable,softwords/plottable,gdseller/plottable,onaio/plottable,iobeam/plottable,palantir/plottable,jacqt/plottable,alyssaq/plottable,softwords/plottable,palantir/plottable,alyssaq/plottable,onaio/plottable,jacqt/plottable,danmane/plottable,alyssaq/plottable,NextTuesday/plottable,gdseller/plottable,iobeam/plottable,palantir/plottable,palantir/plottable,danmane/plottable,NextTuesday/plottable,iobeam/plottable,danmane/plottable,RobertoMalatesta/plottable,jacqt/plottable,onaio/plottable