message: Focus context menus so screen readers can find them
  Fixes
  The `tabIndex` is required to make the thing actually focusable. This is the same trick employed in
diff: @@ -20,6 +20,7 @@ import React from 'react';
  import ReactDOM from 'react-dom';
  import PropTypes from 'prop-types';
  import classNames from 'classnames';
  +import {focusCapturedRef} from "../../utils/Accessibility";
  // Shamelessly ripped off Modal.js. There's probably a better way
  // of doing reusable widgets like dialog boxes & menus where we go and
  @@ -83,6 +84,9 @@ export default class ContextualMenu extends React.Component {
  // We don't need to clean up when unmounting, so ignore
  if (!element) return;
  + // For screen readers to find the thing
  + focusCapturedRef(element);
  +
  this.setState({
  contextMenuRect: element.getBoundingClientRect(),
  });
  @@ -206,7 +210,7 @@ export default class ContextualMenu extends React.Component {
  // FIXME: If a menu uses getDefaultProps it clobbers the onFinished
  // property set here so you can't close the menu from a button click!
  return <div className={className} style={{...position, ...wrapperStyle}}>
  - <div className={menuClasses} style={menuStyle} ref={this.collectContextMenuRect}>
  + <div className={menuClasses} style={menuStyle} ref={this.collectContextMenuRect} tabIndex={0}>
  { chevron }
  <ElementClass {...props} onFinished={props.closeMenu} onResize={props.windowResize} />
  </div>
  