Add mappings to jump to the previous and next domain in a tab.
Add mappings to jump to the previous and next domain in a tab.

Mimics Pentadactyl's functionality, with the same '[d' and ']d'
mappings. This uses the TabHistory structure, which isn't perfect but
does the trick for as long as the extension has been running.

1995eaton/chromium-vim,aplaice/chromium-vim,1995eaton/chromium-vim,aplaice/chromium-vim,1995eaton/chromium-vim,aplaice/chromium-vim,1995eaton/chromium-vim,aplaice/chromium-vim