Linux: use MessageLoopProxy instead of base::Thread in our DBus client library.

Linux: use MessageLoopProxy instead of base::Thread in our DBus client library. 

This allows us to use BrowserThread::GetMessageLoopProxyForThread() to specify the DBus thread.
Also do a little bit of unrelated comment cleanup. 
BUG=90036
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=99794

[Mike Mammarella, 2011-09-04 19:23:51]

http://codereview.chromium.org/7800023/diff/1/dbus/bus.cc
File dbus/bus.cc (left):

http://codereview.chromium.org/7800023/diff/1/dbus/bus.cc#oldcode191
dbus/bus.cc:191: if (dbus_thread_) {
These DCHECKs are the only thing really "lost" in this change. I did not see any
way to check that the actual thread behind the message loop proxy is running, or
to examine its type. (Note that we can still check if we are on it, because
MessageLoopProxy does provide that.)

[satorux1, 2011-09-06 17:15:57]

Thank you for the patch. I like the idea of MessageLoopProxy.

http://codereview.chromium.org/7800023/diff/1/dbus/bus.cc
File dbus/bus.cc (left):

http://codereview.chromium.org/7800023/diff/1/dbus/bus.cc#oldcode191
dbus/bus.cc:191: if (dbus_thread_) {
On 2011/09/04 19:23:52, Mike Mammarella wrote:
> These DCHECKs are the only thing really "lost" in this change. I did not see
any
> way to check that the actual thread behind the message loop proxy is running,
or
> to examine its type. (Note that we can still check if we are on it, because
> MessageLoopProxy does provide that.)

Never mind. The program will fail soon, if the message loop proxy is used
incorrectly. For instance, MessageLoopForIO::current() used in Watch class will
fail if the type is not IO.

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h
File dbus/bus.h (right):

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode84
dbus/bus.h:84: //   bool success = !!response.get();
Thank you for updating this!

!! is a bit tricky. Something like this may be more useful as example code:

  if (response.get()) {  // Success.
    ...

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode160
dbus/bus.h:160: // BrowserThread::GetMessageLoopProxyForThread().
I like the idea of using MessageLoopProxy.

The name |dbus_thread| may be a bit irrelevant. It's a bit long but what about
dbus_thread_message_loop_proxy? Then, I think you can remove the excuse about
the type of dbus_thread.

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode165
dbus/bus.h:165: // 3) Outlives the bus.
3) may be now irrelevant, as MessageLoopProxy takes care of the lifetime
problem.

[Mike Mammarella, 2011-09-06 19:11:08]

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h
File dbus/bus.h (right):

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode84
dbus/bus.h:84: //   bool success = !!response.get();
On 2011/09/06 17:15:57, satorux1 wrote:
> Thank you for updating this!
> 
> !! is a bit tricky. Something like this may be more useful as example code:
> 
>   if (response.get()) {  // Success.
>     ...

Done.

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode160
dbus/bus.h:160: // BrowserThread::GetMessageLoopProxyForThread().
On 2011/09/06 17:15:57, satorux1 wrote:
> I like the idea of using MessageLoopProxy.
> 
> The name |dbus_thread| may be a bit irrelevant. It's a bit long but what about
> dbus_thread_message_loop_proxy? Then, I think you can remove the excuse about
> the type of dbus_thread.

Done.

http://codereview.chromium.org/7800023/diff/1/dbus/bus.h#newcode165
dbus/bus.h:165: // 3) Outlives the bus.
On 2011/09/06 17:15:57, satorux1 wrote:
> 3) may be now irrelevant, as MessageLoopProxy takes care of the lifetime
> problem.

Done.

[satorux1, 2011-09-06 19:28:53]

LGTM!

BTW, you might want to add a blank line after the first line in the patch
description to follow the git convention, as we are switching to the git
workflow.

% git commit --help

DISCUSSION
       Though not required, it´s a good idea to begin the commit message with
       a single short (less than 50 character) line summarizing the change,
       followed by a blank line and then a more thorough description. Tools
       that turn commits into email, for example, use the first line on the
       Subject: line and the rest of the commit in the body.