title: HTTPS page was not allowed to run insecure content from safari-extension:// URI
body: <p>I face a strange behavior in a Safari extension with Safari 9.1 (11601.5.17.1). I try to insert a new Iframe with an src pointing to an html file in the extension package using "safari-extension://...".</p>
  
  <p>The URL is correct and the content is displayed in a new tab, if I click on the link from the error message displayed in the console.</p>
  
  <blockquote>
    <p>[blocked] The page at https:// was not allowed to run
    insecure content from
    safari-extension://com.mycompany.myextension-7KZE138RQQ/3d4c3273/js/proxy.js.</p>
  </blockquote>
  
  <p>It seems the URL with safari-extension scheme is not considered as secured and safari applies "no http in https page" security policy.
  It used to work before (before what? I don't know.).</p>
  
  <p>Any idea? Could that behavior be changed with a specific Content-security-policy?</p>
  
  <p>Thanks</p>