Handle Security Key requests from outside the remoted session correctly

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 aac24e07ca5917238d301eddddeb084bb7415d48..a2ac6057efa6bf29b7753f331b164a98a4e14ab6 100644
--- a/remoting/host/chromoting_messages.h
+++ b/remoting/host/chromoting_messages.h
@@ -252,7 +252,13 @@ IPC_MESSAGE_CONTROL1(ChromotingRemoteSecurityKeyToNetworkMsg_Request,
 // Chromoting messages sent from the network process to the remote_security_key
 // process.
 
-// The array of bytes representing a security key response from the remote
-// client.  This message is sent over the per-client IPC channel.
+// The array of bytes representing the security key response from the client.
 IPC_MESSAGE_CONTROL1(ChromotingNetworkToRemoteSecurityKeyMsg_Response,
                      std::string /* response bytes */)
+
+// Indicates the channel used for security key message passing is ready for use.
+IPC_MESSAGE_CONTROL0(ChromotingNetworkToRemoteSecurityKeyMsg_ConnectionReady)
+
+// Error indicating the request originated from outside the remoted session.
+// The IPC channel will be disconnected after this message has been sent.
+IPC_MESSAGE_CONTROL0(ChromotingNetworkToRemoteSecurityKeyMsg_InvalidSession)