 - decidePolicyForNavigationAction 
<NSURLRequest URL data:text/html,    <iframe id='iframe' src='<p>FAILURE</p>'></iframe>, main document URL iframe-src-invalid-url.html, http method GET> is main frame - no should open URLs externally - no
 - decidePolicyForNavigationAction 
<NSURLRequest URL about:blank, main document URL iframe-src-invalid-url.html, http method GET> is main frame - no should open URLs externally - no
Test passes if the second iframe navigates to about:blank.