Revert of ipc: Clean up interface of attachment broker.

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 4a3eb9d59dbaf853394e04393d93883e8e745190..1dd5702a229db75110c4ce97e0959f24c866ec29 100644
--- a/ipc/ipc_channel_posix.cc
+++ b/ipc/ipc_channel_posix.cc
@@ -955,10 +955,6 @@
   return GetPeerPID();
 }
 
-bool ChannelPosix::IsAttachmentBrokerEndpoint() {
-  return is_attachment_broker_endpoint();
-}
-
 void ChannelPosix::Close() {
   // Close can be called multiple time, so we need to make sure we're
   // idempotent.