sort: {[scale]: channel} doesn’t work when combined with a transform

[mbostock]

E.g., here:

Plot.plot({
  color: {
    legend: true
  },
  marks: [
    Plot.dot(olympians, Plot.sort("height", {
      x: "height",
      y: "weight",
      stroke: "nationality",
      sort: {
        color: "stroke", // we don’t need a channel here; TODO null?
        reduce: "count",
        reverse: true,
        limit: 10
      }
    }))
  ]
})

The addition of the sort transform should look more similar to the below, i.e., without affecting the imputed domain of the color scale; it should only affect the z-order of dots sorted by the height column.

Plot.plot({
  color: {
    legend: true
  },
  marks: [
    Plot.dot(olympians, {
      x: "height",
      y: "weight",
      stroke: "nationality",
      sort: {
        color: "stroke",
        reduce: "count",
        reverse: true,
        limit: 10
      }
    })
  ]
})

Maybe something wrong around here?

plot/src/channel.js

Line 102 in fd18371

range(XV),

Same issue as #840, I think.