[debug] add exception predictions to builtins where missing.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index bac61301c6a465bab8257b91e2c1dbbebd84471f..28ee66525e4a5590fea073bc8734c5482dc1d851 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1351,6 +1351,9 @@ HandlerTable::CatchPrediction PredictException(JavaScriptFrame* frame) {
           if (code->GetCode()->is_exception_caught()) {
             return HandlerTable::CAUGHT;
           }
+
+          // The built-in must be marked with an exception prediction.
+          UNREACHABLE();
         }
 
         if (code->kind() == AbstractCode::OPTIMIZED_FUNCTION) {