title: jQuery.ajax call fails inside Chrome extension
body: <p>I'm porting one of my Firefox extensions to Chrome, and I'm running into a little problem with an AJAX query. The following code works fine in the FF extension, but fails with a status of "0" in Chrome.</p>
  
  <pre><code>function IsImage(url) {
      var isImage = false;
      var reImageContentType = /image\/(jpeg|pjpeg|gif|png|bmp)/i;
      var reLooksLikeImage = /\.(jpg|jpeg|gif|png|bmp)/i;
  
      if(!reLooksLikeImage.test(url)) 
      {
          return false;
      }
  
      var xhr = $.ajax({
          async: false,
          type: "HEAD",
          url: url,
          timeout: 1000,
          complete : function(xhr, status) {
              switch(status)
              {
                  case "success":
                      isImage = reImageContentType.test(xhr.getResponseHeader("Content-Type"));
                      break;
              }
          },
      });
  
      return isImage;
  }
  </code></pre>
  
  <p>This particular part of the extension checks what's on the clipboard (another Chrome issue I've already solved), and if it's an image URL, it sends a HEAD request and checks the "Content-Type" response header to be sure it's an image. If so, it'll return true, pasting the clipboard text in an IMG tag. Otherwise, if it looks like a normal URL that's not an image, it wraps it in an A tag. If it's not a URL, it just does a plain paste.</p>
  
  <p>Anyway, the url being checked is definitely an image, and works fine in FF, but in the complete function, xhr.status is "0", and status is "error" when the function completes. Upping the timeout to 10 seconds doesn't help. I've verified the test images should come back as "image/jpeg" when running:</p>
  
  <pre><code>curl -i -X HEAD &lt;imageURL&gt;
  </code></pre>
  
  <p>I also know I should be using the success and error callbacks instead of complete, but they don't work either. Any ideas?</p>