title: Creating unsafe browser XUL element from Firefox extension gives (NS_ERROR_FAILURE) [nsIWebNavigation.sessionHistory]
body: <p>I'm trying to add hidden <code>browser</code> element dynamically from Firefox extension but, although it adds successfully, it gives me <code>Error: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIWebNavigation.sessionHistory]"  nsresult: "0x80004005 (NS_ERROR_FAILURE)"  location: "JS frame :: chrome://global/content/bindings/browser.xml ::  :: line 641"  data: no]
  Source File: chrome://global/content/bindings/browser.xml
  Line: 647</code></p>
  
  <p>Code looks like this:</p>
  
  <pre><code>let parent = document.querySelector("#browser");
  let browser = document.createElement("browser");
  browser.style.visibility = "hidden";
  parent.appendChild(browser);
  </code></pre>
  
  <p>What I'm doing wrong here?</p>