title: Click event not firing when React Component in a Shadow DOM
body: <p>I have a special case where I need to encapsulate a React Component with a Web Component.  The setup seems very straight forward.  Here is the React Code:</p>
  
  <pre><code>// React Component
  class Box extends React.Component {
    handleClick() {
      alert("Click Works");
    }
    render() {
      return (
        &lt;div 
          style={{background:'red', margin: 10, width: 200, cursor: 'pointer'}} 
          onClick={e =&gt; this.handleClick(e)}&gt;
  
          {this.props.label} &lt;br /&gt; CLICK ME
  
        &lt;/div&gt;
      );
    }
  };
  
  // Render React directly
  ReactDOM.render(
    &lt;Box label="React Direct" /&gt;,
    document.getElementById('mountReact')
  );
  </code></pre>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div id="mountReact"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>This mounts fine and the click event works.  Now when I created a Web Component wrapper around the React Component, it renders correctly but the click event doesn't work.  Here is my Web Component Wrapper:</p>
  
  <pre><code>// Web Component Wrapper
  class BoxWebComponentWrapper extends HTMLElement {
    createdCallback() {
      this.el      = this.createShadowRoot();
      this.mountEl = document.createElement('div');
      this.el.appendChild(this.mountEl);
  
      document.onreadystatechange = () =&gt; {
        if (document.readyState === "complete") {
          ReactDOM.render(
            &lt;Box label="Web Comp" /&gt;,
            this.mountEl
          );
        }
      };
    }
  }
  
  // Register Web Component
  document.registerElement('box-webcomp', {
    prototype: BoxWebComponentWrapper.prototype
  });
  </code></pre>
  
  <p>And here is the HTML:</p>
  
  <pre><code>&lt;box-webcomp&gt;&lt;/box-webcomp&gt;
  </code></pre>
  
  <p>Is there something I'm missing?  Or does React refuse to work inside a Web Component?  I have seen a library like Maple.JS which does this sort of thing, but their library works.  I feel like I'm missing one small thing.</p>
  
  <p>Here is the CodePen so you can see the problem:</p>
  
  <p><a href="http://codepen.io/homeslicesolutions/pen/jrrpLP" rel="noreferrer">http://codepen.io/homeslicesolutions/pen/jrrpLP</a></p>