Add a new GetInstance() method for singleton classes, take 2.

ipc/ipc_channel_posix.cc

Index: ipc/ipc_channel_posix.cc
diff --git a/ipc/ipc_channel_posix.cc b/ipc/ipc_channel_posix.cc
index bbf137432943d7abfe487f8dacf96828a31823ee..781175e33ac0ff74ce444e7f8f30a4ad94c72e52 100644
--- a/ipc/ipc_channel_posix.cc
+++ b/ipc/ipc_channel_posix.cc
@@ -396,7 +396,7 @@ bool Channel::ChannelImpl::CreatePipe(const std::string& channel_id,
         }
         used_initial_channel = true;
 
-        pipe_ = Singleton<base::GlobalDescriptors>()->Get(kPrimaryIPCChannel);
+        pipe_ = base::GlobalDescriptors::GetInstance()->Get(kPrimaryIPCChannel);
       }
     } else {
       waiting_connect_ = mode == MODE_SERVER;