We purge it [here](https://github.com/facebook/react/blob/b11540ccb2321aeb7259fcf0b3a38aeeea35231d/src/isomorphic/ReactDebugTool.js#L88-L89) but this code doesn’t run because of the [early exit](https://github.com/facebook/react/blob/b11540ccb2321aeb7259fcf0b3a38aeeea35231d/src/isomorphic/ReactDebugTool.js#L53-L57).

Need to fix this and add a test case to make sure we don’t regress on it.

return ReactComponentTreeDevtool.getRootIDs()
      .map(ReactComponentTreeDevtool.getDisplayName);
  }
  function getRegisteredDisplayNames() {
    return ReactComponentTreeDevtool.getRegisteredIDs()
      .map(ReactComponentTreeDevtool.getDisplayName);
  }
  function getTree(rootID, options = {}) {