Forward declare CT structs in ct_serialization.h

net/cert/ct_serialization.h

Index: net/cert/ct_serialization.h
diff --git a/net/cert/ct_serialization.h b/net/cert/ct_serialization.h
index f183247469f9e217e017894b425c8af095127817..fa7ab0c6d45c411403c60c6acb81df918043f971 100644
--- a/net/cert/ct_serialization.h
+++ b/net/cert/ct_serialization.h
@@ -8,10 +8,10 @@
 #include <string>
 #include <vector>
 
+#include "base/memory/ref_counted.h"
 #include "base/strings/string_piece.h"
+#include "base/time/time.h"
 #include "net/base/net_export.h"
-#include "net/cert/signed_certificate_timestamp.h"
-#include "net/cert/signed_tree_head.h"
 
 namespace net {
 
@@ -19,6 +19,11 @@ namespace net {
 // Transparency to/from the TLS wire format encoding.
 namespace ct {
 
+struct DigitallySigned;
+struct LogEntry;
+struct SignedCertificateTimestamp;
+struct SignedTreeHead;
+
 // If |input.signature_data| is less than kMaxSignatureLength, encodes the
 // |input| to |output| and returns true. Otherwise, returns false.
 NET_EXPORT_PRIVATE bool EncodeDigitallySigned(const DigitallySigned& input,