daemon: fix PropertiesChanged signal emission

daemon: fix PropertiesChanged signal emission

This fixes a few problems of PropertiesChanged signal emission.
First, it should be sent only when the properties have changed.
Second, invalidated_properties should be set when the properties have
been reset, not on error.  Finally, the sender should be
"org.freedesktop.IBus" rather than "org.freedesktop.DBus".

BUG=
R=takao.fujiwara1@gmail.com

Committed: 583bfe6

[Daiki Ueno, 2013-07-24 04:10:32]

For https://codereview.appspot.com/11422043/, I looked at the set/get properties
code in ibusimpl.c, and noticed that the current code is confusing.

Aside from the issues I mentioned in the commit log, it has:

- unused "connection" parameter for all _ibus_*_{get,set}_*.

- redundant GError clear in all callees, e.g. if (error) { *error = NULL; }.  It
is caller's responsibility to clear it:
https://developer.gnome.org/glib/stable/glib-Error-Reporting.html
I haven't seen that in IBus nor any other GNOME code.

- inconsistent coding style used in bus_ibus_impl_service_{get,set}_property
than bus_ibus_impl_service_method_call.

[Peng, 2013-07-24 14:24:39]

+Fujiwara-san for review

[Peng, 2013-07-24 14:27:32]

On 2013/07/24 14:24:39, Peng wrote:
> +Fujiwara-san for review

Look good to me. But please let Fujiwara-san have a look. He implemented this
piece of code. Thanks.

[fujiwara, 2013-07-25 05:20:04]

LGTM.
Looks good.

On 2013/07/24 04:10:32, Daiki Ueno wrote:
> - unused "connection" parameter for all _ibus_*_{get,set}_*.

Originally I put _ibus_set_global_engine in set_property but it was changed
during the review.
I thought the functions will be updated again when the deprecated functions are
deleted but it's also ok to update those at present.

> - redundant GError clear in all callees, e.g. if (error) { *error = NULL; }. 
It
> is caller's responsibility to clear it:
> https://developer.gnome.org/glib/stable/glib-Error-Reporting.html
> I haven't seen that in IBus nor any other GNOME code.

I have no specific opinion.

> - inconsistent coding style used in bus_ibus_impl_service_{get,set}_property
> than bus_ibus_impl_service_method_call.

Actually I'm fixing the style one by one for other compilers in all files. I'd
like to update bus_ibus_impl_service_method_call in the future.

[Daiki Ueno, 2013-07-25 09:12:35]

Committed patchset #2 manually as r583bfe6 (presubmit successful).