Deletes all features from the layer.
This method works only with redline layers.
Depending on the state of the selection changed flag, calling this method on features in the current selection may fire the onSelectionChanged event.
This method always refreshes the map when the autoRefresh flag is set to True or when called from the onViewChanging or onViewChanged events. Note that this method does not work during a busy state.
boolean - Returns True if successful; otherwise, returns False.
-3 (illegal argument)
-15 (does not apply -- not a redline layer)