Canonicalize handles for optimized compilation.

src/json-stringifier.h

Index: src/json-stringifier.h
diff --git a/src/json-stringifier.h b/src/json-stringifier.h
index c06256d4d737faf9bc0958ed38ff71dd67e03a06..fb990d460738b29182f6da80de3dc6fd3b4841dc 100644
--- a/src/json-stringifier.h
+++ b/src/json-stringifier.h
@@ -222,6 +222,7 @@ MaybeHandle<Object> BasicJsonStringifier::StringifyString(
     SerializeStringUnchecked_(object->GetFlatContent().ToOneByteVector(),
                               &no_extend);
     no_extend.Append('\"');
+    return no_extend.Finalize();
   } else {
     result = isolate->factory()
                  ->NewRawTwoByteString(worst_case_length)
@@ -232,8 +233,8 @@ MaybeHandle<Object> BasicJsonStringifier::StringifyString(
     SerializeStringUnchecked_(object->GetFlatContent().ToUC16Vector(),
                               &no_extend);
     no_extend.Append('\"');
+    return no_extend.Finalize();
   }
-  return result;
 }