Comment 2 for bug 939657

I've noticed for the last few days that whilst running Thunderbird Daily, dbus-daemon will use a lot of CPU for a few minutes every now and again and power consumption goes through the roof. When I look at traffic on the session bus, I see thousands of these messages from Thunderbird:

method call sender=:1.527 -> dest=org.freedesktop.DBus serial=34074 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=AddMatch
   string "type='signal',interface='ca.desrt.dconf.Writer',path='/ca/desrt/dconf/Writer/user',arg0path='/system/proxy/'"

What is happening is that each time we look for the system proxy settings, we are calling g_settings_new(). When doing this, the dconf backend sets up a watch on these settings to be notified of change events.

Of course, there might actually be a Thunderbird bug here, but we can probably improve this situation in nsUnixSystemProxySettings by not creating a new GSettings instance (and not setting up a new watch) each time we look up the proxy settings.