Certificate Transparency: Parse Signed Tree Heads and validate them

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 96268e4d0222ce0ec92a7b9dbc2ae00ed2e21634..9f80144d1d6ce9f2c4c90cd0866a746d3cdebf4f 100644
--- a/net/cert/signed_certificate_timestamp.h
+++ b/net/cert/signed_certificate_timestamp.h
@@ -66,6 +66,12 @@ struct NET_EXPORT_PRIVATE DigitallySigned {
   DigitallySigned();
   ~DigitallySigned();
 
+  // Returns true if |other_hash_algorithm| and |other_signature_algorithm|
+  // match this DigitallySigned hash and signature algorithms.
+  bool SignatureParametersMatch(
+      HashAlgorithm other_hash_algorithm,
+      SignatureAlgorithm other_signature_algorithm) const;
+
   HashAlgorithm hash_algorithm;
   SignatureAlgorithm signature_algorithm;
   // 'signature' field.