**Do you want to request a *feature* or report a *bug*?**

Bug

### Current Behaviour

 - `ReactDOMServer.renderToString` is mutating CSS Variable names that are inlined and in the `--camelCase` format into `--kebab-case`

### Expected Behaviour

 - `ReactDOMServer.renderToString` does not mutate the CSS Variable name, and keeps it in `--camelCase` format

### Demo

 - https://codesandbox.io/s/react-dom-server-debugging-28xsr

### Versions:

 - Issue appears in `react@16.8.6` &  `react-dom@16.8.6` 
 - Issue appears in `react@16.0.0` & `react-dom@16.0.0` 
 - (That's all I've tested so far)

### Other notes:

 - It's worth noting that `ReactDOM.render` is preserving the CSS Variable name and not mutating it. It only seems to only be an issue with `ReactDOMServer.renderToString`

enqueueReplaceState: function(publicInstance, completeState) {
        replace = true;
        queue = [completeState];
      },
      enqueueSetState: function(publicInstance, currentPartialState) {
        if (queue === null) {
          warnNoop(publicInstance, 'setState');
          return null;
        }
        queue.push(currentPartialState);
      },
    };
    let inst;
    if (shouldConstruct(Component)) {
      inst = new Component(element.props, publicContext, updater);
      if (typeof Component.getDerivedStateFromProps === 'function') {
        if (__DEV__) {
          if (inst.state === null || inst.state === undefined) {
            const componentName = getComponentName(Component) || 'Unknown';
            if (!didWarnAboutUninitializedState[componentName]) {
              warningWithoutStack(
                false,
                '`%s` uses `getDerivedStateFromProps` but its initial state is ' +
                  '%s. This is not recommended. Instead, define the initial state by ' +
                  'assigning an object to `this.state` in the constructor of `%s`. ' +
                  'This ensures that `getDerivedStateFromProps` arguments have a consistent shape.',
                componentName,
                inst.state === null ? 'null' : 'undefined',
                componentName,
              );