Add Certificate Transparency logs auditing

components/certificate_transparency/log_dns_client.cc

Index: components/certificate_transparency/log_dns_client.cc
diff --git a/components/certificate_transparency/log_dns_client.cc b/components/certificate_transparency/log_dns_client.cc
index fabbbac4698c36a0e36c9d5690f38ab9aa85587a..e60634b84672824bf1b9963adb114fb848743d9e 100644
--- a/components/certificate_transparency/log_dns_client.cc
+++ b/components/certificate_transparency/log_dns_client.cc
@@ -323,6 +323,30 @@ net::Error LogDnsClient::AuditProofQuery::RequestAuditProofNodes() {
       proof_->nodes.size() >= net::ct::CalculateAuditPathLength(
                                   proof_->leaf_index, proof_->tree_size)) {
     return net::ERR_UNEXPECTED;
+    // The performance of this could be improved by sending all of the expected
+    // queries up front. Each response can contain a maximum of 7 audit path
+    // nodes,
+    // so for an audit proof of size 20, it could send 3 queries (for nodes 0-6,
+    // 7-13 and 14-19) immediately. Currently, it sends only the first and then,
+    // based on the number of nodes received, sends the next query. The
+    // complexity
+    // of the code would increase though, as it would need to detect gaps in the
+    // audit proof caused by the server not responding with the anticipated
+    // number
+    // of nodes. Ownership of the proof would need to change, as it would be
+    // shared
+    // between simultaneous DNS transactions.
+    /*
+    void LogDnsClient::QueryAuditProof(base::StringPiece domain_for_log,
+                                       uint64_t leaf_index,
+                                       uint64_t tree_size,
+                                       const AuditProofCallback& callback) {
+      if (domain_for_log.empty() || leaf_index >= tree_size) {
+        base::ThreadTaskRunnerHandle::Get()->PostTask(
+            FROM_HERE,
+            base::Bind(callback, net::Error::ERR_INVALID_ARGUMENT, nullptr));
+        return;
+    */
   }
 
   std::string qname = base::StringPrintf(