// Sets |value| to the dictionary for |key| if it exists and has a dictionary
// value. Returns false if the key doesn't exist or doesn't correspond to a
// dictionary. The JSON object must be parsed successfully in ParseObject()
- // before invoking this method.
+ // before invoking this method. |value| is only guaranteed to be valid as long
+ // as |this| is valid.
virtual bool GetJsonValueForKey(const std::string& key,
scoped_ptr<Json>* value) const = 0;