Slide recreates style object property

[marlowww]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior

Slide component always recreates children style object and sets its visibility field to 'hidden' / undefined.
In such situation we cannot use neither React.memo (without compare function) nor React.PureComponent, cause function shallowEquals always returns false.

https://github.com/mui-org/material-ui/blob/5c84559ce012e403d01773112774de56d7e74723/packages/material-ui/src/Slide/Slide.js#L212-L222

Expected Behavior

Slide should try to use original style objects whenever it can.

Something like that, should be enough:

// Trying to get children style without recreating style object
const getChildrenStyle = (state) => {
  const forwardedStyle = (() => {
    if (!style) {
      return children.props.style;
    }
    if (!children.props.style) {
      return style;
    }
    return {...style, ...children.props.style};
  })();

  if (state === 'exited' && !inProp) {
    return {visibility: "hidden", ...forwardedStyle}
  }
  return forwardedStyle;
};

Steps to Reproduce

https://codesandbox.io/s/serene-easley-ll4ut

Your Environment

Tech	Version
Material-UI	v4.9.0
React	latest
Browser	chrome