Use ChannelMojo between app shims and the browser process.

mojo/edk/system/node_controller.cc

Index: mojo/edk/system/node_controller.cc
diff --git a/mojo/edk/system/node_controller.cc b/mojo/edk/system/node_controller.cc
index 253af8763d1dee55ad30de36c095fe095ec2fa90..072d92b10391fd0abb112e38e8121577ee3031ca 100644
--- a/mojo/edk/system/node_controller.cc
+++ b/mojo/edk/system/node_controller.cc
@@ -1269,9 +1269,13 @@ void NodeController::OnAcceptPeer(const ports::NodeName& from_node,
   pending_peers_.erase(it);
   DCHECK(channel);
 
-  DVLOG(1) << "Node " << name_ << " accepted peer " << peer_name;
+  // If the peer connection is a self connection (which is used in tests),
+  // drop the channel to it and skip straight to merging the ports.
+  if (name_ != peer_name) {
+    DVLOG(1) << "Node " << name_ << " accepted peer " << peer_name;
 
-  AddPeer(peer_name, channel, false /* start_channel */);
+    AddPeer(peer_name, channel, false /* start_channel */);
+  }
 
   // We need to choose one side to initiate the port merge. It doesn't matter
   // who does it as long as they don't both try. Simple solution: pick the one