chrome.runtime.onInstalled.addListener(function() {
  chrome.declarativeContent.onPageChanged.removeRules(undefined,function() {
    chrome.declarativeContent.onPageChanged.addRules([{
      conditions: [
        // When a page contains a <video> tag...
        new chrome.declarativeContent.PageStateMatcher({
          pageUrl: { hostEquals: 'www.youtube.com'}
        })
      ],// ... show the page action.
      actions: [new chrome.declarativeContent.ShowPageAction() ]
    }]);
  });

});

我得到了无法在控制台中读取未定义的属性’onPageChanged’.运行代码没问题,为什么会这样？