file.href

[mbostock]

Fixes #954.

[Fil]

Would it be useful to make this discoverable in the inspector?

For example by adding a getter to FileAttachmentImpl:

  get href() {
    return this.href;
  }

(it would also be nice to hide the deprecated url() method, but I don't know how to do that.)

[mbostock]

If we want the file.href to be discoverable, we simply make it enumerable here:

    Object.defineProperty(this, "href", {value: href, enumerable: true});

I chose not to do that because I think it’s extra noise, but let me take a look and see what I think.