Material-ui: Dialogs: missing backdrop css API

[nicgirault]

I can't find a way to customize the css of a backdrop/overlay of a dialog.

• [x] I have searched the issues of this repository and believe that this is not a duplicate.

| Tech | Version |
|--------------|---------|
| Material-UI | v1.0.0-rc.0 |

[oliviertassinari]

      <Dialog
        BackdropProps={{
          className: classes.backdrop
        }}

https://codesandbox.io/s/03mj318xm0

[oliviertassinari]

@nicgirault The trick is to follow the properties inheritance / cascading between the components.
Dialog > Modal

[TrySound]

But classes api allows to handle it in less noisy way

const UDialog = withStyles({
  backgrop: {
    background: '#000'
  }
})(Dialog)