net: add DnsRRResovler to fetch arbitary DNS resource types.

net/base/dns_util.h

Index: net/base/dns_util.h
diff --git a/net/base/dns_util.h b/net/base/dns_util.h
index cd814202ae8d898a6ae7d3342970f425a6802fa0..88c48a8bbbc7cf63e4619cdea59646e185b77160 100644
--- a/net/base/dns_util.h
+++ b/net/base/dns_util.h
@@ -8,6 +8,8 @@
 
 #include <string>
 
+#include "base/basictypes.h"
+
 namespace net {
 
 // DNSDomainFromDot - convert a domain string to DNS format. From DJB's
@@ -24,6 +26,14 @@ bool IsSTD3ASCIIValidCharacter(char c);
 // Returns the hostname by trimming the ending dot, if one exists.
 std::string TrimEndingDot(const std::string& host);
 
+// DNS resource record types. See
+// http://www.iana.org/assignments/dns-parameters
+
+static const uint16 kDNS_TXT = 16;
+static const uint16 kDNS_RRSIG = 46;
+static const uint16 kDNS_CERT = 37;
+static const uint16 kDNS_ANY = 0xff;
+
 }  // namespace net
 
 #endif  // NET_BASE_DNS_UTIL_H_