Call darray.compute() in plot() (#3183)
Call darray.compute() in plot() (#3183)

* Call darray.compute() in plot()

* review.

markelg/xray,pydata/xarray,markelg/xray,xray/xray,shoyer/xarray,jhamman/xarray,markelg/xray,shoyer/xarray,jhamman/xarray,pydata/xarray,jhamman/xray,pydata/xarray,jhamman/xarray