Use ChannelMojo for remote security key channels.

remoting/host/chromoting_messages.h

Index: remoting/host/chromoting_messages.h
diff --git a/remoting/host/chromoting_messages.h b/remoting/host/chromoting_messages.h
index 42e77868a4e51a5ab3a7160bdfc04279578129bf..5ee40f92b525ca1f085b78314862149599cc6aa7 100644
--- a/remoting/host/chromoting_messages.h
+++ b/remoting/host/chromoting_messages.h
@@ -249,22 +249,7 @@ IPC_MESSAGE_CONTROL1(ChromotingRemoteSecurityKeyToNetworkMsg_Request,
 
 //---------------------------------------------------------
 // Chromoting messages sent from the network process to the remote_security_key
-// process.  The network process uses two types of IPC channels to communicate
-// with the remote_security_key process.  The first is the 'service' channel.
-// It uses a hard-coded path known by the client and server classes and its job
-// is to create a new, private IPC channel for the client and provide the path
-// to that channel over the original IPC channel.  This purpose for this
-// mechanism is to allow the network process to service multiple concurrent
-// security key requests.  Once a client receives the connection details for
-// its private IPC channel, the server channel is reset and can be called by
-// another client.
-// The second type of IPC channel is strictly used for passing security key
-// request and response messages.  It is destroyed once the client disconnects.
-
-// The IPC channel path for this remote_security_key connection.  This message
-// is sent from the well-known IPC server channel.
-IPC_MESSAGE_CONTROL1(ChromotingNetworkToRemoteSecurityKeyMsg_ConnectionDetails,
-                     std::string /* IPC Server path */)
+// process.
 
 // The array of bytes representing a security key response from the remote
 // client.  This message is sent over the per-client IPC channel.