Create new function in contentScriptFile in Firefox extension

interfaces components/mycomponent.xpt
binary-component components/mycomponent.dll ABI=WINNT_x86-msvc

var form = document.createElementNS('http://www.w3.org/1999/xhtml', 'form');

const { Ci, Cu, Cc, Cr } = require('chrome'); //const {interfaces: Ci, utils: Cu, classes: Cc, results: Cr } = Components;
Cu.import('resource://gre/modules/Services.jsm');
Cu.import('resource://gre/modules/devtools/Console.jsm');

var observers = {
    'http-on-modify-request': {
        observe: function (aSubject, aTopic, aData) {
            console.info('http-on-modify-request: aSubject = ' + aSubject + ' | aTopic = ' + aTopic + ' | aData = ' + aData);
            var httpChannel = aSubject.QueryInterface(Ci.nsIHttpChannel);
            var requestUrl = httpChannel.URI.spec
            var goodies = loadContextAndGoodies(aSubject, true);
            if (goodies.contentWindow) {
               if (goodies.contentWindow == CONTENT_WINDOW_OF_CONTENT_SCRIPT) {
                    //do something here
               }
            }
        },
        reg: function () {
            Services.obs.addObserver(observers['http-on-modify-request'], 'http-on-modify-request', false);
        },
        unreg: function () {
            Services.obs.removeObserver(observers['http-on-modify-request'], 'http-on-modify-request');
        }
    }
};

function loadContextAndGoodies(request, return_goodies) {
  var loadContext = null;

  if (request instanceof Ci.nsIRequest) {
      try {
          if (request.loadGroup && request.loadGroup.notificationCallbacks) {
              loadContext = request.loadGroup.notificationCallbacks.getInterface(Ci.nsILoadContext);
          }
      } catch (ex) {
        console.exception('request loadGroup with notificationCallbacks but oculd not get nsIloadContext', ex);
      }
      if (!loadContext) {
        try {
            if (request.notificationCallbacks) {
                loadContext = request.notificationCallbacks.getInterface(Ci.nsILoadContext);
            }
        } catch (ex) {
          console.exception('request has notificationCallbacks but could not get nsILoadContext', ex);
          /* start - noit's backup try, it might be redundant (im not sure) as Wladamir Palant didn't have this way*/
          try {
            var interfaceRequestor = httpChannel.notificationCallbacks.QueryInterface(Ci.nsIInterfaceRequestor);
            loadContext = interfaceRequestor.getInterface(Ci.nsILoadContext);
          } catch (ex) {
            console.exception('backup method failed:' ex);
          }
          /* end - my backup try, it might be redundant as Wladamir Palant didn't have this way*/
        }
      }
  } else {
    console.warn('request argument is not instance of nsIRequest')
  }

  if (return_goodies) {
    if (!loadContext) {
      return null;
    }

    var contentWindow = loadContext.associatedWindow;
    var DOMWindow = contentWindow.top.QueryInterface(Ci.nsIInterfaceRequestor)
                                     .getInterface(Ci.nsIWebNavigation)
                                     .QueryInterface(Ci.nsIDocShellTreeItem)
                                     .rootTreeItem
                                     .QueryInterface(Ci.nsIInterfaceRequestor)
                                     .getInterface(Ci.nsIDOMWindow);
    var gBrowser = DOMWindow.gBrowser;
    if (gBrowser) {
      var tab = gBrowser._getTabForContentWindow(contentWindow.top);
      var browser = tab.linkedBrowser;
    } else {
      var tab, browser = null;
    }
    var goodies = {
      loadContext: loadContext,
      DOMWindow: DOMWindow,
      gBrowser: gBrowser,
      contentWindow: contentWindow,
      browser: browser,
      tab: tab
    };

    return goodies;
  } else {
    return loadContext;
  }
}

for (var o in observers) {
    observers[o].reg();
}

for (var o in observers) {
    observers[o].unreg();
}

var selection = document.getSelection();
var range = selection.getRangeAt(0);

var ancestorContainer = range.commonAncestorContainer;

var nodeIterator = document.createNodeIterator(
  // first argument is the root node at which to begin the NodeIterator's traversal:
 ancestorContainer,
 // second argument 'whatToShow'; we're interested in elements:
 NodeFilter.SHOW_ELEMENT,
 // third argument 'filter', a function whose return value tells iterator which nodes to iterate over.
 function (node) {
  return selection.containsNode(node) ? NodeFilter.FILTER_ACCEPT : NodeFilter.FILTER_REJECT;
 }
);

var elementsWithinSelection = [];
var e = nodeIterator.nextNode();
while (e) {
 elementsWithinSelection.push(e);
 e = nodeIterator.nextNode();
}

self.postMessage(JSON.stringify(elementsWithinSelection.map(function (e) {
 return e.outerHTML;
})));