Return reference to WebStringCpp that is managed by reference-counting in WebString.
If this is not initialized yet,
WebStringCpp is initialized by $(awebview.wrapper.cpp.WebString.init).
If this is const or immutable and this is not initialized yet,
this method returns a reference to global empty instance of immutable(WebStringCpp).
// ditto
Return reference to WebStringCpp that is managed by reference-counting in WebString.
If this is not initialized yet, WebStringCpp is initialized by $(awebview.wrapper.cpp.WebString.init).
If this is const or immutable and this is not initialized yet, this method returns a reference to global empty instance of immutable(WebStringCpp). // ditto