[SpeedDialAction] Follow the classes root convention (#13634)

* Allow styling of the tooltip

* use the root convention

Author: DrPhil

packages/material-ui-lab/src/SpeedDialAction/SpeedDialAction.js

@@ -7,6 +7,8 @@ import Fab from '@material-ui/core/Fab';
 import Tooltip from '@material-ui/core/Tooltip';
 
 export const styles = theme => ({
+  /* Styles applied to the root element. */
+  root: {},
   /* Styles applied to the `Button` component. */
   button: {
     margin: 8,
@@ -101,6 +103,7 @@ class SpeedDialAction extends React.Component {
         placement={tooltipPlacement}
         onClose={this.handleTooltipClose}
         onOpen={this.handleTooltipOpen}
+        className={classes.root}
         open={open && this.state.tooltipOpen}
         {...other}
       >

pages/lab/api/speed-dial-action.md

@@ -36,6 +36,7 @@ This property accepts the following keys:
 
 | Name | Description |
 |:-----|:------------|
+| <span class="prop-name">root</span> | Styles applied to the root element.
 | <span class="prop-name">button</span> | Styles applied to the `Button` component.
 | <span class="prop-name">buttonClosed</span> | Styles applied to the `Button` component if `open={false}`.