title: ClickHandler get clicked element
body: <p>When I'm adding a clickhandler to a button, im doing it like this:</p>
  
  <pre><code>button.addClickHandler(myHandler);
  
  // myHandler
  public void onClick(ClickEvent event) {
      // how to get the button here?
  }
  </code></pre>
  
  <p>Does anyone know how I can get the button object that has been clicked inside the clickhandler?</p>