remoting: Add AttachmentBroker for daemon and desktop processes

remoting/host/daemon_process.cc

Index: remoting/host/daemon_process.cc
diff --git a/remoting/host/daemon_process.cc b/remoting/host/daemon_process.cc
index 1d5fcd466126eebedea36d9a874a69a5982378f7..b0a8228861a7cdc3eb6788db8bd37461c1c3b990 100644
--- a/remoting/host/daemon_process.cc
+++ b/remoting/host/daemon_process.cc
@@ -15,6 +15,7 @@
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
+#include "ipc/attachment_broker_privileged.h"
 #include "net/base/net_util.h"
 #include "remoting/base/auto_thread_task_runner.h"
 #include "remoting/host/branding.h"
@@ -183,6 +184,8 @@ DaemonProcess::DaemonProcess(
       stopped_callback_(stopped_callback),
       weak_factory_(this) {
   DCHECK(caller_task_runner->BelongsToCurrentThread());
+
+  IPC::AttachmentBrokerPrivileged::CreateBrokerIfNeeded();

[joedow, 2016/01/26 21:42:51]

It looks like this method has different args for OSX and I believe this file is
compiled into our mac host.  Does this need a conditional around it for OSX vs.
other host builds?

[erikchen, 2016/01/26 21:47:00]

Oh, yes. The Chrome browser process, on Mac, has a Port Provider
(base::PortProvider) which provides the task port of its child processes. This
is also required for attachment brokering. I'm surprised this hasn't broken on
Mac since we've been passing Mach SharedMemoryHandles on Mac since M49.

[Sergey Ulanov, 2016/01/27 01:38:39]

There are some files like this one that are compiled only on platform that don't
use multi-process hosts (i.e. OSX and Linux). This is mainly so that this code
can be unittested on all platforms and to make it easier to enabled
multi-process when necessary.
IPC::AttachmentBrokerPrivileged::CreateBrokerIfNeeded() doesn't do anything on
Linux, but we can still call it. OSX does need attachment broker.

[Sergey Ulanov, 2016/01/27 01:43:02]

We are not using this code on OSX.

Updated this code to compile on OSX now.

Erik, is it possible to update CreateBrokerIfNeeded() to
callMachBroker::GetInstance()? then initialization here wouldn't need to be
platform-specific

[erikchen, 2016/01/27 15:16:41]

If this code isn't being used on OSX, why is it being compiled on OSX? I'm
hesitant to make changes that make it easier to incorrectly use an API. It
doesn't make sense to instantiate a privileged AttachmentBroker without a Mach
broker.

Can we just wrap this in !defined(OS_MACOSX)?

[Sergey Ulanov, 2016/01/27 18:29:12]

The goal is to implement multi-process host on OSX as well, and maybe eventually
on Linux.
Done.

 }
 
 void DaemonProcess::CreateDesktopSession(int terminal_id,