Refuse to resolve some types of invalid DNS addresses.

net/dns/dns_util.cc

Index: net/dns/dns_util.cc
diff --git a/net/dns/dns_util.cc b/net/dns/dns_util.cc
index 48be035c0e3380d37f5aa0d29e3406760b97db6d..217aedc50010252bde6c50459220751e0163f4c6 100644
--- a/net/dns/dns_util.cc
+++ b/net/dns/dns_util.cc
@@ -83,6 +83,11 @@ bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
   return true;
 }
 
+bool IsValidDNSDomain(const base::StringPiece& dotted) {
+  std::string dns_formatted;
+  return DNSDomainFromDot(dotted, &dns_formatted);
+}
+
 std::string DNSDomainToString(const base::StringPiece& domain) {
   std::string ret;