Bug 380744, Thunderbird reports "unable to decrypt" on truncated decryptable messages

r=relyea, sr=mscott

security/manager/ssl/public/nsICMSMessageErrors.idl

@@ -63,6 +63,7 @@ interface nsICMSMessageErrors : nsISupports
   const long VERIFY_CERT_WITHOUT_ADDRESS = 1040;
 
   const long ENCRYPT_NO_BULK_ALG = 1056;
+  const long ENCRYPT_INCOMPLETE = 1057;
 };
 
 %{ C++
@@ -118,4 +119,7 @@ interface nsICMSMessageErrors : nsISupports
 #define NS_ERROR_CMS_ENCRYPT_NO_BULK_ALG \
   NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, \
                             nsICMSMessageErrors::ENCRYPT_NO_BULK_ALG)
+#define NS_ERROR_CMS_ENCRYPT_INCOMPLETE \
+  NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, \
+                            nsICMSMessageErrors::ENCRYPT_INCOMPLETE)
 %}