BarTabWebProgressListener.onStateChange vs browser.webNavigation._pauseLoadURI is not a function

prototypes.js

/*
 * Progress listener that stops the loading of tabs that are opened in
 * the background and whose contents is loaded by C++ code.  This
 * occurs for instance when the 'browser.tabs.loadDivertedInBackground'
 * preference is enabled (because links are always opened by docshell code).
 */
function BarTabWebProgressListener () {}
BarTabWebProgressListener.prototype = { 
    ...
  /*** nsIWebProgressListener ***/

  onStateChange: function (aWebProgress, aRequest, aStateFlags, aStatus) { 
   ...
    
   // panorama switch
    if (this._tab._tabViewTabItem && 
        this._tab._tabViewTabItem.parent && 
        this._tab._tabViewTabItem.parent._activeTab.tab  && 
        this._tab._tabViewTabItem.parent._activeTab.tab == this._tab
      ) {
      this._tab.removeAttribute("ontab");
      // webNavigation.unhook() will call our unhook.
      browser.webNavigation.unhook();
      return;
    }
     
    ...
   }
   
   ...