[NOT FOR REVIEW] Ensure contributory behaviour for Web Push encryption.

components/gcm_driver/crypto/gcm_message_cryptographer.h

Index: components/gcm_driver/crypto/gcm_message_cryptographer.h
diff --git a/components/gcm_driver/crypto/gcm_message_cryptographer.h b/components/gcm_driver/crypto/gcm_message_cryptographer.h
index e2b299e5860b45fd544e5463da1ff8dde271bfb4..fa52e43109d000bad4a1cafdfa072ed67beec788 100644
--- a/components/gcm_driver/crypto/gcm_message_cryptographer.h
+++ b/components/gcm_driver/crypto/gcm_message_cryptographer.h
@@ -36,7 +36,8 @@ class GCMMessageCryptographer {
   // unique content encryption key for a given message.
   static const size_t kSaltSize;
 
-  GCMMessageCryptographer();
+  GCMMessageCryptographer(const base::StringPiece& local_public_key,
+                          const base::StringPiece& peer_public_key);
   ~GCMMessageCryptographer();
 
   // Encrypts |plaintext| using the |key| and the |salt|, both of which must be
@@ -83,6 +84,12 @@ class GCMMessageCryptographer {
   // Derives the nonce from |key| and |salt|.
   std::string DeriveNonce(const base::StringPiece& key,
                           const base::StringPiece& salt) const;
+
+  // The context. TODO: Better comment.
+  std::string nonce_info_;
+  std::string content_encryption_key_info_;
+
+  std::string context_;
 };
 
 }  // namespace gcm