List message decryption failures on chrome://gcm-internals

components/gcm_driver/crypto/gcm_encryption_provider.h

Index: components/gcm_driver/crypto/gcm_encryption_provider.h
diff --git a/components/gcm_driver/crypto/gcm_encryption_provider.h b/components/gcm_driver/crypto/gcm_encryption_provider.h
index c545276830675daac047e9739bf84ddfc2a5f478..9eec22cd9063c0060f279607879e9a30f76df134 100644
--- a/components/gcm_driver/crypto/gcm_encryption_provider.h
+++ b/components/gcm_driver/crypto/gcm_encryption_provider.h
@@ -58,6 +58,9 @@ class GCMEncryptionProvider {
   // Callback to be invoked when a message cannot be decoded.
   using DecryptionFailedCallback = base::Callback<void(DecryptionFailure)>;
 
+  // Converts |reason| to a string describing the details of said reason.
+  static std::string ToDecryptionFailureDetailsString(DecryptionFailure reason);
+
   GCMEncryptionProvider();
   ~GCMEncryptionProvider();