legacy_propagate_error

If this is a SimpleAsyncResult, this is equivalent to propagate_error.

Otherwise it returns false.

This can be used for legacy error handling in async *_finish() wrapper functions that traditionally handled SimpleAsyncResult error returns themselves rather than calling into the virtual method. This should not be used in new code; AsyncResult errors that are set by virtual methods should also be extracted by virtual methods, to enable subclasses to chain up correctly.

Parameters:

this	a AsyncResult

Returns:

true if throws is has been filled in with an error from this, false if not.