Set correct g-flags to proxy objects.

Set correct g-flags to proxy objects.

This change is similar to https://github.com/ibus/ibus/commit/19247aac5a348185a0e180f254ab3858c5f85703.

The flag can prevent unnecessary communications between ibus-daemon and e.g. engines like this:

$ . ~/.config/ibus/bus/*-unix-0 ; dbus-monitor --address $IBUS_ADDRESS 2>&1 | tee /tmp/ibus.log
...
method call sender=org.freedesktop.DBus -> dest=(null destination) serial=3 path=/org/freedesktop/IBus/Factory; interface=org.freedesktop.IBus.Factory; member=CreateEngine
   string "mozc-jp"
method return sender=:1.15 -> dest=org.freedesktop.DBus reply_serial=3
   object path "/org/freedesktop/IBus/Engine/1"
method call sender=org.freedesktop.DBus -> dest=(null destination) serial=4 path=/org/freedesktop/IBus/Engine/1; interface=org.freedesktop.DBus.Properties; member=GetAll
   string "org.freedesktop.IBus.Engine"
method return sender=:1.15 -> dest=org.freedesktop.DBus reply_serial=4
   array [
   ]

Calling an engine's org.freedesktop.DBus.Properties.GetAll method when the engine is created is unnecessary for ibus-daemon, while it's not harmful though.

BUG=none
TEST=verified using dbus-monitor that ibus-daemon does not call GetAll anymore.

[Peng, 2011-01-16 00:53:30]

On 2011/01/16 00:02:02, Yusuke Sato wrote:

Currently it is not useful. But in future, maybe we will use properties for
preedit text, lookup table and etc. Anyway we could disable it right now.

LGTM