Revert of ipc: Clean up interface of attachment broker.

ipc/attachment_broker_unprivileged.cc

Index: ipc/attachment_broker_unprivileged.cc
diff --git a/ipc/attachment_broker_unprivileged.cc b/ipc/attachment_broker_unprivileged.cc
index b84eea398f4202693c4a3524d8fba7aae8ba72b5..bc2eb5a764dbf0dfafa61ea5286bbc04d1b4bb70 100644
--- a/ipc/attachment_broker_unprivileged.cc
+++ b/ipc/attachment_broker_unprivileged.cc
@@ -3,8 +3,6 @@
 // found in the LICENSE file.
 
 #include "ipc/attachment_broker_unprivileged.h"
-
-#include "ipc/ipc_channel.h"
 
 namespace IPC {
 
@@ -12,12 +10,4 @@
 
 AttachmentBrokerUnprivileged::~AttachmentBrokerUnprivileged() {}
 
-void AttachmentBrokerUnprivileged::DesignateBrokerCommunicationChannel(
-    IPC::Channel* channel) {
-  DCHECK(channel);
-  DCHECK(!sender_);
-  sender_ = channel;
-  channel->set_attachment_broker_endpoint(true);
-}
-
 }  // namespace IPC