Snackbar is using a <p> after upgrading to 3.2

I upgraded to 3.2 and set useNextVariants: true and the Snackbar component started using a <p> element for its container, which throws a warning in the browser if you have a <div> as a child.

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

Snackbar should use a <div> as its container element.

Current Behavior

Snackbar is using a <p> as its container element.

Steps to Reproduce

Open the live example (https://codesandbox.io/s/82wp5l1jkl) and check the console logs. You’ll see

Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.
    in div (created by App)
    in div (created by SnackbarContent)
    in p (created by Typography)
    in Typography (created by WithStyles(Typography))
    in WithStyles(Typography) (created by Paper)
    in Paper (created by WithStyles(Paper))
    in WithStyles(Paper) (created by SnackbarContent)
    in SnackbarContent (created by WithStyles(SnackbarContent))
    in WithStyles(SnackbarContent) (created by Snackbar)
    in Transition (created by Slide)
    in EventListener (created by Slide)
    in Slide (created by WithTheme(Slide))
    in WithTheme(Slide) (created by Snackbar)
    in div (created by Snackbar)
    in ClickAwayListener (created by Snackbar)
    in Snackbar (created by WithStyles(Snackbar))
    in WithStyles(Snackbar) (created by App)
    in MuiThemeProvider (created by App)
    in App

Here is the same example working with v3.1.2: https://codesandbox.io/s/32p389xr15

I’m guessing it has something to do with this line: https://github.com/mui-org/material-ui/blob/master/packages/material-ui/src/SnackbarContent/SnackbarContent.js#L55. I’m not passing in a variant for the Typography component, so I don’t think the headlineMapping is getting applied.

I was able to work around this bug by doing:

<Snackbar
  ContentProps={{
    variant: `body1`,
  }}
/>

Your Environment

Tech	Version
Material-UI	v3.2.0
React	16.5.2
Browser	Chrome

[eps1lon]

While a fix in HEAD is good I failed to add a temporary workaround for everyone affected:

https://codesandbox.io/s/248j265l5r:

-<Snackbar message={<div>Testing</div>} open />
+<Snackbar ContentProps={{
+      headlineMapping: {
+        body1: "div",
+        body2: "div"
+      }
+    }} message={<div>Testing</div>} open />

Basically add to ContentProps the headlineMapping conforming to the above shape.

[eps1lon]

@brauliodiez Sorry I need to manage by sandboxes better. I had to delete everything recently because I reached the free usage limit.

Updated link: https://codesandbox.io/s/zz6wnqklzm (demo.js#71-74)