Flash object context menu extension from addon?

Question

Mozilla

Good morning, habr!
Faced a difficulty in expanding the context menu (by the right mouse button gets out) for a flash-object.
This is happening in the context of an addon on a fresh firefox addon SDK .
The code is something like this:

var CONTEXT_MENU = require("sdk/context-menu");
var menuItem = CONTEXT_MENU.Item({
  context: CONTEXT_MENU.URLContext(['*.dsga.me',]), 
  contentScriptFile: self.data.url('context-menu-actions.js'),
  onMessage: function(text) {
    var searchUrl = "http://dseye.ru/service/addon-search.html?term=" + require("sdk/querystring").escape(text);
    TABS.open(searchUrl);
  }
});

and generally not far gone from the canonical manual.
The problem is that the context menu of third-party objects (and the flash is third-party, because the plugin is separate) does not expand this code =(
Diligent Google did not find a solution, and so I came to you.
Thanks in advance.