Update proto to have a field for error type

Test: unit tests
Bug: 153374987
Change-Id: I80f2758e740e530c501e363d3caf137fc1f3cf9e
diff --git a/proto/test_record.proto b/proto/test_record.proto
index 96553c7..6f5a6ae 100644
--- a/proto/test_record.proto
+++ b/proto/test_record.proto
@@ -127,4 +127,7 @@
 
   // A free-formed text that can help debugging the issue at hand.
   string debug_help_message = 10;
-}
\ No newline at end of file
+
+  // The fully-qualified name of the exception class associated with the error.
+  string error_type = 20;
+}