[Dialog] Simplify the DialogContentText implementation

packages/material-ui/src/DialogContentText/DialogContentText.js

@@ -2,30 +2,16 @@
 
 import React from 'react';
 import PropTypes from 'prop-types';
-import classNames from 'classnames';
 import withStyles from '../styles/withStyles';
 import Typography from '../Typography';
 
-export const styles = theme => ({
+export const styles = {
   /* Styles applied to the root element. */
-  root: {
-    color: theme.palette.text.secondary,
-  },
-});
+  root: {},
+};
 
 function DialogContentText(props) {
-  const { children, classes, className, ...other } = props;
-
-  return (
-    <Typography
-      component="p"
-      variant="subheading"
-      className={classNames(classes.root, className)}
-      {...other}
-    >
-      {children}
-    </Typography>
-  );
+  return <Typography component="p" variant="subheading" color="textSecondary" {...props} />;
 }
 
 DialogContentText.propTypes = {
@@ -38,10 +24,6 @@ DialogContentText.propTypes = {
    * See [CSS API](#css-api) below for more details.
    */
   classes: PropTypes.object.isRequired,
-  /**
-   * @ignore
-   */
-  className: PropTypes.string,
 };
 
 export default withStyles(styles, { name: 'MuiDialogContentText' })(DialogContentText);