a11y - Focus not moved to verification window when opened

[GoogleCodeExporter]

On latest fully patched OS X with Voiceover running with Safari.

Actioning the checkbox will sometimes bring up a "verification window" which is 
a series of images. Focus is not always moved to the newly inserted UI element. 
Other times it is moved but lands on the "get a new challenge" button instead 
of the top. Other times the typical verification window to identify some fuzzy 
text is popped up. Focus is moved here but nothing is announced other than 
"Type The Text" because focus lands on the initial input which has no 
instructive label. Getting a new challenge does not move focus to the newly 
added content.

Original issue reported on code.google.com by [email protected] on 4 Jun 2015 at 2:24