Add helpers to figure out what is logged where

The logic to figure out what logger and what service should be logging
what is a bit annoying and tricky.  Do it in a function so we can test
it easily.

Change-Id: Ia493fcabd7529a7235941d49462172c9988ce07f
diff --git a/aos/configuration.h b/aos/configuration.h
index ab235a3..7bf8203 100644
--- a/aos/configuration.h
+++ b/aos/configuration.h
@@ -65,6 +65,18 @@
 // provided node.
 bool ChannelIsReadableOnNode(const Channel *channel, const Node *node);
 
+// Returns true if the message is supposed to be logged on this node.
+bool ChannelMessageIsLoggedOnNode(const Channel *channel, const Node *node);
+
+const Connection *ConnectionToNode(const Channel *channel, const Node *node);
+// Returns true if the delivery timestamps are supposed to be logged on this
+// node.
+bool ConnectionDeliveryTimeIsLoggedOnNode(const Channel *channel,
+                                          const Node *node,
+                                          const Node *logger_node);
+bool ConnectionDeliveryTimeIsLoggedOnNode(const Connection *connection,
+                                          const Node *node);
+
 // Prints a channel to json, but without the schema.
 std::string CleanedChannelToString(const Channel *channel);