Use a forward declaration of RSAPrivateKey in crypto/signature_creator.h.

crypto/signature_creator.h

Index: crypto/signature_creator.h
===================================================================
--- crypto/signature_creator.h	(revision 120638)
+++ crypto/signature_creator.h	(working copy)
@@ -22,7 +22,6 @@
 
 #include "base/basictypes.h"
 #include "crypto/crypto_export.h"
-#include "crypto/rsa_private_key.h"
 
 #if defined(OS_WIN)
 #include "crypto/scoped_capi_types.h"
@@ -30,6 +29,8 @@
 
 namespace crypto {
 
+class RSAPrivateKey;
+
 // Signs data using a bare private key (as opposed to a full certificate).
 // Currently can only sign data using SHA-1 with RSA encryption.
 class CRYPTO_EXPORT SignatureCreator {