function change() {
    var xmlDom = Blockly.Xml.workspaceToDom(workspace);
    var xmlText = Blockly.Xml.domToText(xmlDom);
    if (startXmlText != xmlText) {
      window.location.hash = '';
      workspace.removeChangeListener(bindData);
    }
  }
Start monitoring the workspace.  If a change is made that changes the XML,
clear the key from the URL.  Stop monitoring the workspace once such a
change is detected.
@param {!Blockly.WorkspaceSvg} workspace Workspace.
@private