Open Radar

 
Summary: 
When a PDF with the header "Content-Disposition: attachment" is downloaded from within Mobile Safari, the Safari Page loses its securityOrigin and all subsequent AJAX requests on that domain fail with the following error message:
"XMLHTTPRequest cannot load http://example.com/path/ajax.php. Cannot make any requests from null".
It seems to be failing at line 105 of http://opensource.apple.com/source/WebCore/WebCore-1298/loader/CrossOriginAccessControl.cpp 
Opening the PDF in a New Page or closing the original page and making requests from a new one fixes the issue. 

Steps to Reproduce:
1) On iOS 5.0 or 5.0.1, go to http://timtrinidad.com/ajaxtest. Click on file.pdf under "Content-disposition: attachment" to open PDF in the browser.
2) Click Back
3) Reload the original page

Expected Results:
After the reload, the page loads the AJAX response.

Actual Results:
No AJAX response is loaded; the following error is thrown in the console:
JavaScript: Error on Line 1
XMLHttpRequest cannot load http://timtrinidad.com/ajaxtest/ajax.php. Cannot make any requests from null.

Regression:

Notes:
The test source code is in the attached zip files. All other files on the page work without issue.