setLibraryDebuggable abstract method
setLibraryDebuggable RPC is used to enable or disable whether
breakpoints and stepping work for a given library.
isolateId refers to an isolate which has exited, then the
Sentinel is returned.
This method will throw a SentinelException in the case a Sentinel is returned.
Future<Success> setLibraryDebuggable( String isolateId, String libraryId, bool isDebuggable);