title: Chrome Tabs.CaptureVisibleTab is Undefined
body: <p>I'm trying to create a pop-up that will display the visible tab as a small image. The <em>ImgSrc</em> returned from the chrome.tabs.captureVisibleTab() function is "Undefined". I have tried running this from various places. I can verify that the tab returned from the tabs.Query() is not-null, so the tabs[0].id is not null.</p>
  
  <p>Am I doing this incorrectly?</p>
  
  <p>Here's my manifest, popup.html and popup.js files:</p>
  
  <pre><code>{
    "manifest_version": 2,
  
    "name": "SuperFave",
    "description": "Saves favorites demo",
    "version": "1.0",
  
    "browser_action": {
      "default_popup": "popup.html"
    },
  
    "permissions": [
      "tabs",
      "&lt;all_urls&gt;"
    ]
  }
  </code></pre>
  
  <p>popup.html:</p>
  
  <pre><code>&lt;html&gt;
    &lt;head&gt;
      &lt;script type="text/javascript" src="jquery-1.10.2.min.js"&gt;
      &lt;/script&gt;
      &lt;script type="text/javascript" src="popup.js"&gt;
      &lt;/script&gt;
    &lt;/head&gt;
    &lt;body&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>popup.js:</p>
  
  <pre><code>$(document).ready( function () {
    chrome.tabs.query( {
        // gets the window the user can currently see
        active: true, 
        currentWindow: true 
      },
      function (tabs) {
        chrome.tabs.captureVisibleTab( 
          tabs[0].id,
          function (src) {
            // displays a link to the image. Can be replaced by an alert() to 
            // verify the result is 'undefined'
            $('body').append("&lt;a href='" + src + "'&gt;" + tabs[0].url + "&lt;/a&gt;");
          }
        ); 
      }
    );
  });
  </code></pre>