title: Chrome extention - using current tab's window function from background
body: <p>I am using content script and background script.
  On tab loading a function is added to the <code>window</code> object.
  I will use this example:
   <code>window.myFunc = function() {...};</code></p>
  
  <p>I need to use myFunction from the background script, but because background is running on diffrent <code>window</code> -  <code>myFunc</code> is not accessible </p>
  
  <p>How can I use <code>myFunc</code> from the background script?</p>