Adds a function for encoding a Merkle tree leaf in TLS wire format.

net/cert/signed_certificate_timestamp.h

Index: net/cert/signed_certificate_timestamp.h
diff --git a/net/cert/signed_certificate_timestamp.h b/net/cert/signed_certificate_timestamp.h
index 02697dc7a1fe6ce8da113a011ba84d38d6b7e841..db7f671db069fcddb50c160cfeb88fcab5c9c122 100644
--- a/net/cert/signed_certificate_timestamp.h
+++ b/net/cert/signed_certificate_timestamp.h
@@ -93,6 +93,8 @@ struct NET_EXPORT SignedCertificateTimestamp
 
   // Version enum in RFC 6962, Section 3.2.
   enum Version {
+    // TODO(robpercival): Fix inconsistent naming between this,
+    // MerkleTreeLeaf::Version and SignedTreeHead::Version.
     SCT_VERSION_1 = 0,
   };