Two changes to the DBus C++ library.

Two changes to the DBus C++ library.

- Added GetPrivateBusConnection() which is necessary to implement language switcher integrated with Chrome (http://bit.ly/8LUDJE). We have to make a DBus connection for the language switcher private, since im_ibus.so (GTK_IM_MODULE for Chrome) establishes a DBus connection to the same address and the IM module does not expect that the connection is shared with other code in the same process. If we don't make the connection private, im_ibus.so dies with g_assert.
- Added another constructor to the Proxy class so that the language switcher can connect to IME candidate window using ::::dbus_g_proxy_new_for_name_owner() API.

This change is for http://codereview.chromium.org/460107

BUG=494

[Yusuke Sato, 2009-12-08 07:03:49]

Can you please review this? This small change is necessary to implement the
IME/language switcher for Chrome OS
(http://dev.chromium.org/chromium-os/chromiumos-design-docs/text-input/demos).

[Sean Parent, 2009-12-10 17:38:20]

http://codereview.chromium.org/465097/diff/1/2
File src/common/chromeos/dbus/dbus.cc (right):

http://codereview.chromium.org/465097/diff/1/2#newcode13
src/common/chromeos/dbus/dbus.cc:13: bool is_g_bus_get_called = false;
This looks like a thread unsafe hack - I know dbus is a big mess, but is there a
better way to handle this?

http://codereview.chromium.org/465097/diff/1/2#newcode67
src/common/chromeos/dbus/dbus.cc:67: ::dbus_g_bus_get(DBUS_BUS_SYSTEM,
&Resetter(&error).lvalue());
I believe you are leaking this connection and the application will be terminated
when the connection is closed from the other end (which happens before chrome
quits). See comment in GetSystemBusConnection() above. Perhaps just always call
GetSystemBusConnection() here to force the standard marshalers to get
initialized.

http://codereview.chromium.org/465097/diff/1/2#newcode74
src/common/chromeos/dbus/dbus.cc:74: 
I don't know what the ownership rules are on this connection. Do you need to
unref? If ownership is transfered on one of the next calls then write a comment
to that effect.

http://codereview.chromium.org/465097/diff/1/3
File src/common/chromeos/dbus/dbus.h (right):

http://codereview.chromium.org/465097/diff/1/3#newcode91
src/common/chromeos/dbus/dbus.h:91: Init(connection, name, path, interface,
connect_to_name_owner);
If Init() is instead written as a stand alone function returning a ::DBusGProxy*
then you can use member initialization here.

http://codereview.chromium.org/465097/diff/1/3#newcode136
src/common/chromeos/dbus/dbus.h:136: void Init(const BusConnection& connection,
Make this a regular function and move the implementation to the .cc file.

[Yusuke Sato, 2009-12-11 11:57:31]

Thanks for the review! Fixed all.

http://codereview.chromium.org/465097/diff/1/2
File src/common/chromeos/dbus/dbus.cc (right):

http://codereview.chromium.org/465097/diff/1/2#newcode13
src/common/chromeos/dbus/dbus.cc:13: bool is_g_bus_get_called = false;
Removed the hack. Since GetPrivateBusConnection() is called just once when
Chrome is launched, probably it's okay to call GetSystemBusConnection()
unconditionally in the GetPrivateBusConnection() function.

http://codereview.chromium.org/465097/diff/1/2#newcode67
src/common/chromeos/dbus/dbus.cc:67: ::dbus_g_bus_get(DBUS_BUS_SYSTEM,
&Resetter(&error).lvalue());
Ah, you're right. Replaced it with GetSystemBusConnection();. Thanks.

http://codereview.chromium.org/465097/diff/1/2#newcode74
src/common/chromeos/dbus/dbus.cc:74: 
Ownership is transferred to |result| on L.76. Added a comment.

http://codereview.chromium.org/465097/diff/1/3
File src/common/chromeos/dbus/dbus.h (right):

http://codereview.chromium.org/465097/diff/1/3#newcode91
src/common/chromeos/dbus/dbus.h:91: Init(connection, name, path, interface,
connect_to_name_owner);
Sure. Created "private: static value_type GetGProxy(.....)" member function. Is
this okay for you?

http://codereview.chromium.org/465097/diff/1/3#newcode136
src/common/chromeos/dbus/dbus.h:136: void Init(const BusConnection& connection,
Moved to the .cc file.

[Sean Parent, 2009-12-11 16:32:39]

http://codereview.chromium.org/465097/diff/1/3
File src/common/chromeos/dbus/dbus.h (right):

http://codereview.chromium.org/465097/diff/1/3#newcode147
src/common/chromeos/dbus/dbus.h:147: &error);
I missed this on the first pass, if an error is generated, it is going to leak.
See the use of ScopedError further in this file. It is also useful if you log
the error message when there is an error.

[Yusuke Sato, 2009-12-14 01:35:32]

http://codereview.chromium.org/465097/diff/1/3
File src/common/chromeos/dbus/dbus.h (right):

http://codereview.chromium.org/465097/diff/1/3#newcode147
src/common/chromeos/dbus/dbus.h:147: &error);
Thanks, fixed. Please take another look at the Proxy::GetGProxy() function in
dbus.cc.

[Sean Parent, 2009-12-14 21:03:27]

LGTM