title: AJAX calls inside an iframe inside an extension page
body: <p>I have a chrome extension that displays UI from a web service as its own inside an iframe inside an extension page.  I am injecting some content scripts into the remote UI using:</p>
  
  <pre><code>"content_scripts": [
    {
      "matches" : [ "https://mywebservice.com/frontend/*" ] ,
      "js" : [ "frontend-page-contentscript.js" ],
      "all_frames" : true
    }
  ]
  </code></pre>
  
  <p>Which is allowed because of (also in manifest.json):  [EDIT: This turns out NOT to be required to run content-scripts in the iframe - but removing it doesn't make AJAX work the way I expect].</p>
  
  <pre><code>"sandbox" : {
    "pages" : [
      "cocoon_page_proxy.html"
    ]
  }
  </code></pre>
  
  <p>However, when I make a trivial ajax call (not from the content script, from the iframe):</p>
  
  <pre><code>$.get('asdf',function success(data) { console.log("Success"); },
               function error(xhr) { console.log("Error: "+xhr.responseText); });
  </code></pre>
  
  <p>I don't get any response, it stalls out and gets a "0" for a status.  This (in my experience) is usually due to a cross-origin permissions problem, but it shouldn't be - it's requesting another resource from the same server the main page came from.</p>
  
  <p>Suggestions?</p>