[devtools] prevent Xvfb resets
Seems like firefox opens more than one connection to the X server in
some cases, and things get utterly confused.
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')