mbostock/d3 — pull request #938 by ZJONSSON (2012-12-04 17:22:56+00:00)
Title: Xhr function callback

If d3.xhr is redefined as a function (another way to set the callback) it can be used directly with queue.js without having to wrap inside a bespoke function.
```
queue()
.defer(d3.csv("fileA.csv").get())
.defer(d3.csv("fileB.csv").get())
.await(......
```
For some reason this pull request includes a previous commit (CORS support) by Mike and blends them together. Don't understand why, feel free to just close. In any case the idea here is to remove ` xhr = {}` and replace with `function xhr(callback) { on.load(callback...)}`