Return MaybeHandle from SetElement and DeleteElement.

src/json-parser.h

Index: src/json-parser.h
diff --git a/src/json-parser.h b/src/json-parser.h
index a566402c7362e49928bc79a9c26ea2fd9b4dd715..f7b544c9b5070b6ed460115cb71afb235b9c111e 100644
--- a/src/json-parser.h
+++ b/src/json-parser.h
@@ -360,7 +360,7 @@ Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
           Handle<Object> value = ParseJsonValue();
           if (value.is_null()) return ReportUnexpectedCharacter();
 
-          JSObject::SetOwnElement(json_object, index, value, SLOPPY);
+          JSObject::SetOwnElement(json_object, index, value, SLOPPY).Assert();
           continue;
         }
         // Not an index, fallback to the slow path.