ipc: Use a global for the process's attachment broker.

ipc/attachment_broker_privileged_win_unittest.cc

Index: ipc/attachment_broker_privileged_win_unittest.cc
diff --git a/ipc/attachment_broker_privileged_win_unittest.cc b/ipc/attachment_broker_privileged_win_unittest.cc
index 610921e1039a14202d91a8997e0e3bfb3ce6380f..314252f60fc79a5ab163ba45222cee415b2cd7d1 100644
--- a/ipc/attachment_broker_privileged_win_unittest.cc
+++ b/ipc/attachment_broker_privileged_win_unittest.cc
@@ -220,6 +220,7 @@ class IPCAttachmentBrokerPrivilegedWinTest : public IPCTestBase {
   // Takes ownership of |broker|. Has no effect if called after CommonSetUp().
   void set_broker(IPC::AttachmentBrokerUnprivilegedWin* broker) {
     broker_.reset(broker);
+    IPC::AttachmentBroker::SetGlobal(broker);
   }
 
   void CommonSetUp() {
@@ -424,6 +425,7 @@ int CommonPrivilegedProcessMain(OnMessageReceivedCallback callback,
 
   // Set up IPC channel.
   IPC::AttachmentBrokerPrivilegedWin broker;
+  IPC::AttachmentBroker::SetGlobal(&broker);

[Tom Sepez, 2015/09/11 15:58:30]

This goes out of scope while the process is still alive, seemingly contradicting
the previous comments. Now the process is well on its way to exiting when the
code returns ...

[erikchen, 2015/09/11 20:16:02]

I updated the comment to say:
"""
Each process has at most one attachment broker. The process is responsible
for ensuring that |broker| stays alive for as long as the process is
sending/receiving ipc messages.
"""

   scoped_ptr<IPC::Channel> channel(IPC::Channel::CreateClient(
       IPCTestBase::GetChannelName(channel_name), &listener, &broker));
   broker.RegisterCommunicationChannel(channel.get());