Add a usage pattern bit for host-host connections.

Bug: None
Change-Id: I66dee594295212fcc40a7706f688c9ab15967775
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/149341
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29172}
diff --git a/pc/peer_connection.h b/pc/peer_connection.h
index 550a9ee..b6da82a 100644
--- a/pc/peer_connection.h
+++ b/pc/peer_connection.h
@@ -103,7 +103,13 @@
     // successfully added, either via AddIceCandidate or from the remote
     // description.
     REMOTE_CANDIDATE_ADDED = 0x20000,
-    MAX_VALUE = 0x40000,
+    // An explicit host-host candidate pair is selected, i.e. both the local and
+    // the remote candidates have the host type. This does not include candidate
+    // pairs formed with equivalent prflx remote candidates, e.g. a host-prflx
+    // pair where the prflx candidate has the same base as a host candidate of
+    // the remote peer.
+    DIRECT_CONNECTION_SELECTED = 0x40000,
+    MAX_VALUE = 0x80000,
   };
 
   explicit PeerConnection(PeerConnectionFactory* factory,