I just tried screwing around with the extension switches, and I think I found it.
When I switch YouTube Video and Mp3 Downloader off and refresh the Google page, the Royal stuff doesn't appear, so I guess that was it... Weird. I haven't had problems with it before, but if this plugin really is the culprit, then I guess I'll delete it.
Thanks for your time!
I literally got the same problem with the same exact plugin. uninstalled the plugin and reinstalled it. The adware never came back. I guess it writes itself into the code.