Support the validation of frames and iframes of the current page with the embedded validator.
The tooltip shows the results for all the frames, while the statusbar label the total count.
In the result dialog, show all the results sorted by frame (and then by line, and then column); in case the page has no frames, don't show the "frame" column.

On the code point of view: shuffled a bit some code to keep a list of the validation result objects, instead of a validator.